FreeBSD/Linux Kernel Cross Reference
sys/netinet6/mld6.c

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * Copyright (c) 2009 Bruce Simpson.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. The name of the author may not be used to endorse or promote
     *    products derived from this software without specific prior written
     *    permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      $KAME: mld6.c,v 1.27 2001/04/04 05:17:30 itojun Exp $
     */
    
    /*-
     * Copyright (c) 1988 Stephen Deering.
     * Copyright (c) 1992, 1993
     *      The Regents of the University of California.  All rights reserved.
     *
     * This code is derived from software contributed to Berkeley by
     * Stephen Deering of Stanford University.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)igmp.c      8.1 (Berkeley) 7/19/93
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include "opt_inet.h"
    #include "opt_inet6.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/mbuf.h>
    #include <sys/socket.h>
    #include <sys/sysctl.h>
    #include <sys/kernel.h>
    #include <sys/callout.h>
    #include <sys/malloc.h>
    #include <sys/module.h>
    #include <sys/ktr.h>
    
    #include <net/if.h>
    #include <net/if_var.h>
    #include <net/route.h>
    #include <net/vnet.h>
    
    #include <netinet/in.h>
    #include <netinet/in_var.h>
    #include <netinet6/in6_var.h>
    #include <netinet/ip6.h>
    #include <netinet6/ip6_var.h>
    #include <netinet6/scope6_var.h>
    #include <netinet/icmp6.h>
    #include <netinet6/mld6.h>
    #include <netinet6/mld6_var.h>
    
   #include <security/mac/mac_framework.h>
   
   #ifndef KTR_MLD
   #define KTR_MLD KTR_INET6
   #endif
   
   static void     mli_delete_locked(struct ifnet *);
   static void     mld_dispatch_packet(struct mbuf *);
   static void     mld_dispatch_queue(struct mbufq *, int);
   static void     mld_final_leave(struct in6_multi *, struct mld_ifsoftc *);
   static void     mld_fasttimo_vnet(struct in6_multi_head *inmh);
   static int      mld_handle_state_change(struct in6_multi *,
                       struct mld_ifsoftc *);
   static int      mld_initial_join(struct in6_multi *, struct mld_ifsoftc *,
                       const int);
   #ifdef KTR
   static char *   mld_rec_type_to_str(const int);
   #endif
   static void     mld_set_version(struct mld_ifsoftc *, const int);
   static void     mld_slowtimo_vnet(void);
   static int      mld_v1_input_query(struct ifnet *, const struct ip6_hdr *,
                       /*const*/ struct mld_hdr *);
   static int      mld_v1_input_report(struct ifnet *, const struct ip6_hdr *,
                       /*const*/ struct mld_hdr *);
   static void     mld_v1_process_group_timer(struct in6_multi_head *,
                       struct in6_multi *);
   static void     mld_v1_process_querier_timers(struct mld_ifsoftc *);
   static int      mld_v1_transmit_report(struct in6_multi *, const int);
   static void     mld_v1_update_group(struct in6_multi *, const int);
   static void     mld_v2_cancel_link_timers(struct mld_ifsoftc *);
   static void     mld_v2_dispatch_general_query(struct mld_ifsoftc *);
   static struct mbuf *
                   mld_v2_encap_report(struct ifnet *, struct mbuf *);
   static int      mld_v2_enqueue_filter_change(struct mbufq *,
                       struct in6_multi *);
   static int      mld_v2_enqueue_group_record(struct mbufq *,
                       struct in6_multi *, const int, const int, const int,
                       const int);
   static int      mld_v2_input_query(struct ifnet *, const struct ip6_hdr *,
                       struct mbuf *, struct mldv2_query *, const int, const int);
   static int      mld_v2_merge_state_changes(struct in6_multi *,
                       struct mbufq *);
   static void     mld_v2_process_group_timers(struct in6_multi_head *,
                       struct mbufq *, struct mbufq *,
                       struct in6_multi *, const int);
   static int      mld_v2_process_group_query(struct in6_multi *,
                       struct mld_ifsoftc *mli, int, struct mbuf *,
                       struct mldv2_query *, const int);
   static int      sysctl_mld_gsr(SYSCTL_HANDLER_ARGS);
   static int      sysctl_mld_ifinfo(SYSCTL_HANDLER_ARGS);
   
   /*
    * Normative references: RFC 2710, RFC 3590, RFC 3810.
    *
    * Locking:
    *  * The MLD subsystem lock ends up being system-wide for the moment,
    *    but could be per-VIMAGE later on.
    *  * The permitted lock order is: IN6_MULTI_LOCK, MLD_LOCK, IF_ADDR_LOCK.
    *    Any may be taken independently; if any are held at the same
    *    time, the above lock order must be followed.
    *  * IN6_MULTI_LOCK covers in_multi.
    *  * MLD_LOCK covers per-link state and any global variables in this file.
    *  * IF_ADDR_LOCK covers if_multiaddrs, which is used for a variety of
    *    per-link state iterators.
    *
    *  XXX LOR PREVENTION
    *  A special case for IPv6 is the in6_setscope() routine. ip6_output()
    *  will not accept an ifp; it wants an embedded scope ID, unlike
    *  ip_output(), which happily takes the ifp given to it. The embedded
    *  scope ID is only used by MLD to select the outgoing interface.
    *
    *  During interface attach and detach, MLD will take MLD_LOCK *after*
    *  the IF_AFDATA_LOCK.
    *  As in6_setscope() takes IF_AFDATA_LOCK then SCOPE_LOCK, we can't call
    *  it with MLD_LOCK held without triggering an LOR. A netisr with indirect
    *  dispatch could work around this, but we'd rather not do that, as it
    *  can introduce other races.
    *
    *  As such, we exploit the fact that the scope ID is just the interface
    *  index, and embed it in the IPv6 destination address accordingly.
    *  This is potentially NOT VALID for MLDv1 reports, as they
    *  are always sent to the multicast group itself; as MLDv2
    *  reports are always sent to ff02::16, this is not an issue
    *  when MLDv2 is in use.
    *
    *  This does not however eliminate the LOR when ip6_output() itself
    *  calls in6_setscope() internally whilst MLD_LOCK is held. This will
    *  trigger a LOR warning in WITNESS when the ifnet is detached.
    *
    *  The right answer is probably to make IF_AFDATA_LOCK an rwlock, given
    *  how it's used across the network stack. Here we're simply exploiting
    *  the fact that MLD runs at a similar layer in the stack to scope6.c.
    *
    * VIMAGE:
    *  * Each in6_multi corresponds to an ifp, and each ifp corresponds
    *    to a vnet in ifp->if_vnet.
    */
   static struct mtx                mld_mtx;
   static MALLOC_DEFINE(M_MLD, "mld", "mld state");
   
   #define MLD_EMBEDSCOPE(pin6, zoneid)                                    \
           if (IN6_IS_SCOPE_LINKLOCAL(pin6) ||                             \
               IN6_IS_ADDR_MC_INTFACELOCAL(pin6))                          \
                   (pin6)->s6_addr16[1] = htons((zoneid) & 0xFFFF)         \
   
   /*
    * VIMAGE-wide globals.
    */
   VNET_DEFINE_STATIC(struct timeval, mld_gsrdelay) = {10, 0};
   VNET_DEFINE_STATIC(LIST_HEAD(, mld_ifsoftc), mli_head);
   VNET_DEFINE_STATIC(int, interface_timers_running6);
   VNET_DEFINE_STATIC(int, state_change_timers_running6);
   VNET_DEFINE_STATIC(int, current_state_timers_running6);
   
   #define V_mld_gsrdelay                  VNET(mld_gsrdelay)
   #define V_mli_head                      VNET(mli_head)
   #define V_interface_timers_running6     VNET(interface_timers_running6)
   #define V_state_change_timers_running6  VNET(state_change_timers_running6)
   #define V_current_state_timers_running6 VNET(current_state_timers_running6)
   
   SYSCTL_DECL(_net_inet6);        /* Note: Not in any common header. */
   
   SYSCTL_NODE(_net_inet6, OID_AUTO, mld, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
       "IPv6 Multicast Listener Discovery");
   
   /*
    * Virtualized sysctls.
    */
   SYSCTL_PROC(_net_inet6_mld, OID_AUTO, gsrdelay,
       CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
       &VNET_NAME(mld_gsrdelay.tv_sec), 0, sysctl_mld_gsr, "I",
       "Rate limit for MLDv2 Group-and-Source queries in seconds");
   
   /*
    * Non-virtualized sysctls.
    */
   static SYSCTL_NODE(_net_inet6_mld, OID_AUTO, ifinfo,
       CTLFLAG_RD | CTLFLAG_MPSAFE, sysctl_mld_ifinfo,
       "Per-interface MLDv2 state");
   
   static int      mld_v1enable = 1;
   SYSCTL_INT(_net_inet6_mld, OID_AUTO, v1enable, CTLFLAG_RWTUN,
       &mld_v1enable, 0, "Enable fallback to MLDv1");
   
   static int      mld_v2enable = 1;
   SYSCTL_INT(_net_inet6_mld, OID_AUTO, v2enable, CTLFLAG_RWTUN,
       &mld_v2enable, 0, "Enable MLDv2");
   
   static int      mld_use_allow = 1;
   SYSCTL_INT(_net_inet6_mld, OID_AUTO, use_allow, CTLFLAG_RWTUN,
       &mld_use_allow, 0, "Use ALLOW/BLOCK for RFC 4604 SSM joins/leaves");
   
   /*
    * Packed Router Alert option structure declaration.
    */
   struct mld_raopt {
           struct ip6_hbh          hbh;
           struct ip6_opt          pad;
           struct ip6_opt_router   ra;
   } __packed;
   
   /*
    * Router Alert hop-by-hop option header.
    */
   static struct mld_raopt mld_ra = {
           .hbh = { 0, 0 },
           .pad = { .ip6o_type = IP6OPT_PADN, 0 },
           .ra = {
               .ip6or_type = IP6OPT_ROUTER_ALERT,
               .ip6or_len = IP6OPT_RTALERT_LEN - 2,
               .ip6or_value[0] = ((IP6OPT_RTALERT_MLD >> 8) & 0xFF),
               .ip6or_value[1] = (IP6OPT_RTALERT_MLD & 0xFF)
           }
   };
   static struct ip6_pktopts mld_po;
   
   static __inline void
   mld_save_context(struct mbuf *m, struct ifnet *ifp)
   {
   
   #ifdef VIMAGE
           m->m_pkthdr.PH_loc.ptr = ifp->if_vnet;
   #endif /* VIMAGE */
           m->m_pkthdr.rcvif = ifp;
           m->m_pkthdr.flowid = ifp->if_index;
   }
   
   static __inline void
   mld_scrub_context(struct mbuf *m)
   {
   
           m->m_pkthdr.PH_loc.ptr = NULL;
           m->m_pkthdr.flowid = 0;
   }
   
   /*
    * Restore context from a queued output chain.
    * Return saved ifindex.
    *
    * VIMAGE: The assertion is there to make sure that we
    * actually called CURVNET_SET() with what's in the mbuf chain.
    */
   static __inline uint32_t
   mld_restore_context(struct mbuf *m)
   {
   
   #if defined(VIMAGE) && defined(INVARIANTS)
           KASSERT(curvnet == m->m_pkthdr.PH_loc.ptr,
               ("%s: called when curvnet was not restored: cuvnet %p m ptr %p",
               __func__, curvnet, m->m_pkthdr.PH_loc.ptr));
   #endif
           return (m->m_pkthdr.flowid);
   }
   
   /*
    * Retrieve or set threshold between group-source queries in seconds.
    *
    * VIMAGE: Assume curvnet set by caller.
    * SMPng: NOTE: Serialized by MLD lock.
    */
   static int
   sysctl_mld_gsr(SYSCTL_HANDLER_ARGS)
   {
           int error;
           int i;
   
           error = sysctl_wire_old_buffer(req, sizeof(int));
           if (error)
                   return (error);
   
           MLD_LOCK();
   
           i = V_mld_gsrdelay.tv_sec;
   
           error = sysctl_handle_int(oidp, &i, 0, req);
           if (error || !req->newptr)
                   goto out_locked;
   
           if (i < -1 || i >= 60) {
                   error = EINVAL;
                   goto out_locked;
           }
   
           CTR2(KTR_MLD, "change mld_gsrdelay from %d to %d",
                V_mld_gsrdelay.tv_sec, i);
           V_mld_gsrdelay.tv_sec = i;
   
   out_locked:
           MLD_UNLOCK();
           return (error);
   }
   
   /*
    * Expose struct mld_ifsoftc to userland, keyed by ifindex.
    * For use by ifmcstat(8).
    *
    * VIMAGE: Assume curvnet set by caller. The node handler itself
    * is not directly virtualized.
    */
   static int
   sysctl_mld_ifinfo(SYSCTL_HANDLER_ARGS)
   {
           struct epoch_tracker     et;
           int                     *name;
           int                      error;
           u_int                    namelen;
           struct ifnet            *ifp;
           struct mld_ifsoftc      *mli;
   
           name = (int *)arg1;
           namelen = arg2;
   
           if (req->newptr != NULL)
                   return (EPERM);
   
           if (namelen != 1)
                   return (EINVAL);
   
           error = sysctl_wire_old_buffer(req, sizeof(struct mld_ifinfo));
           if (error)
                   return (error);
   
           IN6_MULTI_LOCK();
           IN6_MULTI_LIST_LOCK();
           MLD_LOCK();
           NET_EPOCH_ENTER(et);
   
           error = ENOENT;
           ifp = ifnet_byindex(name[0]);
           if (ifp == NULL)
                   goto out_locked;
   
           LIST_FOREACH(mli, &V_mli_head, mli_link) {
                   if (ifp == mli->mli_ifp) {
                           struct mld_ifinfo info;
   
                           info.mli_version = mli->mli_version;
                           info.mli_v1_timer = mli->mli_v1_timer;
                           info.mli_v2_timer = mli->mli_v2_timer;
                           info.mli_flags = mli->mli_flags;
                           info.mli_rv = mli->mli_rv;
                           info.mli_qi = mli->mli_qi;
                           info.mli_qri = mli->mli_qri;
                           info.mli_uri = mli->mli_uri;
                           error = SYSCTL_OUT(req, &info, sizeof(info));
                           break;
                   }
           }
   
   out_locked:
           NET_EPOCH_EXIT(et);
           MLD_UNLOCK();
           IN6_MULTI_LIST_UNLOCK();
           IN6_MULTI_UNLOCK();
           return (error);
   }
   
   /*
    * Dispatch an entire queue of pending packet chains.
    * VIMAGE: Assumes the vnet pointer has been set.
    */
   static void
   mld_dispatch_queue(struct mbufq *mq, int limit)
   {
           struct mbuf *m;
   
           while ((m = mbufq_dequeue(mq)) != NULL) {
                   CTR3(KTR_MLD, "%s: dispatch %p from %p", __func__, mq, m);
                   mld_dispatch_packet(m);
                   if (--limit == 0)
                           break;
           }
   }
   
   /*
    * Filter outgoing MLD report state by group.
    *
    * Reports are ALWAYS suppressed for ALL-HOSTS (ff02::1)
    * and node-local addresses. However, kernel and socket consumers
    * always embed the KAME scope ID in the address provided, so strip it
    * when performing comparison.
    * Note: This is not the same as the *multicast* scope.
    *
    * Return zero if the given group is one for which MLD reports
    * should be suppressed, or non-zero if reports should be issued.
    */
   static __inline int
   mld_is_addr_reported(const struct in6_addr *addr)
   {
   
           KASSERT(IN6_IS_ADDR_MULTICAST(addr), ("%s: not multicast", __func__));
   
           if (IPV6_ADDR_MC_SCOPE(addr) == IPV6_ADDR_SCOPE_NODELOCAL)
                   return (0);
   
           if (IPV6_ADDR_MC_SCOPE(addr) == IPV6_ADDR_SCOPE_LINKLOCAL) {
                   struct in6_addr tmp = *addr;
                   in6_clearscope(&tmp);
                   if (IN6_ARE_ADDR_EQUAL(&tmp, &in6addr_linklocal_allnodes))
                           return (0);
           }
   
           return (1);
   }
   
   /*
    * Attach MLD when PF_INET6 is attached to an interface.  Assumes that the
    * current VNET is set by the caller.
    */
   struct mld_ifsoftc *
   mld_domifattach(struct ifnet *ifp)
   {
           struct mld_ifsoftc *mli;
   
           CTR3(KTR_MLD, "%s: called for ifp %p(%s)", __func__, ifp, if_name(ifp));
   
           mli = malloc(sizeof(struct mld_ifsoftc), M_MLD, M_WAITOK | M_ZERO);
           mli->mli_ifp = ifp;
           mli->mli_version = MLD_VERSION_2;
           mli->mli_flags = 0;
           mli->mli_rv = MLD_RV_INIT;
           mli->mli_qi = MLD_QI_INIT;
           mli->mli_qri = MLD_QRI_INIT;
           mli->mli_uri = MLD_URI_INIT;
           mbufq_init(&mli->mli_gq, MLD_MAX_RESPONSE_PACKETS);
           if ((ifp->if_flags & IFF_MULTICAST) == 0)
                   mli->mli_flags |= MLIF_SILENT;
           if (mld_use_allow)
                   mli->mli_flags |= MLIF_USEALLOW;
   
           MLD_LOCK();
           LIST_INSERT_HEAD(&V_mli_head, mli, mli_link);
           MLD_UNLOCK();
   
           return (mli);
   }
   
   /*
    * Hook for ifdetach.
    *
    * NOTE: Some finalization tasks need to run before the protocol domain
    * is detached, but also before the link layer does its cleanup.
    * Run before link-layer cleanup; cleanup groups, but do not free MLD state.
    *
    * SMPng: Caller must hold IN6_MULTI_LOCK().
    * Must take IF_ADDR_LOCK() to cover if_multiaddrs iterator.
    * XXX This routine is also bitten by unlocked ifma_protospec access.
    */
   void
   mld_ifdetach(struct ifnet *ifp, struct in6_multi_head *inmh)
   {
           struct epoch_tracker     et;
           struct mld_ifsoftc      *mli;
           struct ifmultiaddr      *ifma;
           struct in6_multi        *inm;
   
           CTR3(KTR_MLD, "%s: called for ifp %p(%s)", __func__, ifp,
               if_name(ifp));
   
           IN6_MULTI_LIST_LOCK_ASSERT();
           MLD_LOCK();
   
           mli = MLD_IFINFO(ifp);
           IF_ADDR_WLOCK(ifp);
           /*
            * Extract list of in6_multi associated with the detaching ifp
            * which the PF_INET6 layer is about to release.
            */
           NET_EPOCH_ENTER(et);
           CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                   inm = in6m_ifmultiaddr_get_inm(ifma);
                   if (inm == NULL)
                           continue;
                   in6m_disconnect_locked(inmh, inm);
   
                   if (mli->mli_version == MLD_VERSION_2) {
                           in6m_clear_recorded(inm);
   
                           /*
                            * We need to release the final reference held
                            * for issuing the INCLUDE {}.
                            */
                           if (inm->in6m_state == MLD_LEAVING_MEMBER) {
                                   inm->in6m_state = MLD_NOT_MEMBER;
                                   in6m_rele_locked(inmh, inm);
                           }
                   }
           }
           NET_EPOCH_EXIT(et);
           IF_ADDR_WUNLOCK(ifp);
           MLD_UNLOCK();
   }
   
   /*
    * Hook for domifdetach.
    * Runs after link-layer cleanup; free MLD state.
    *
    * SMPng: Normally called with IF_AFDATA_LOCK held.
    */
   void
   mld_domifdetach(struct ifnet *ifp)
   {
   
           CTR3(KTR_MLD, "%s: called for ifp %p(%s)",
               __func__, ifp, if_name(ifp));
   
           MLD_LOCK();
           mli_delete_locked(ifp);
           MLD_UNLOCK();
   }
   
   static void
   mli_delete_locked(struct ifnet *ifp)
   {
           struct mld_ifsoftc *mli, *tmli;
   
           CTR3(KTR_MLD, "%s: freeing mld_ifsoftc for ifp %p(%s)",
               __func__, ifp, if_name(ifp));
   
           MLD_LOCK_ASSERT();
   
           LIST_FOREACH_SAFE(mli, &V_mli_head, mli_link, tmli) {
                   if (mli->mli_ifp == ifp) {
                           /*
                            * Free deferred General Query responses.
                            */
                           mbufq_drain(&mli->mli_gq);
   
                           LIST_REMOVE(mli, mli_link);
   
                           free(mli, M_MLD);
                           return;
                   }
           }
   }
   
   /*
    * Process a received MLDv1 general or address-specific query.
    * Assumes that the query header has been pulled up to sizeof(mld_hdr).
    *
    * NOTE: Can't be fully const correct as we temporarily embed scope ID in
    * mld_addr. This is OK as we own the mbuf chain.
    */
   static int
   mld_v1_input_query(struct ifnet *ifp, const struct ip6_hdr *ip6,
       /*const*/ struct mld_hdr *mld)
   {
           struct ifmultiaddr      *ifma;
           struct mld_ifsoftc      *mli;
           struct in6_multi        *inm;
           int                      is_general_query;
           uint16_t                 timer;
   #ifdef KTR
           char                     ip6tbuf[INET6_ADDRSTRLEN];
   #endif
   
           NET_EPOCH_ASSERT();
   
           is_general_query = 0;
   
           if (!mld_v1enable) {
                   CTR3(KTR_MLD, "ignore v1 query %s on ifp %p(%s)",
                       ip6_sprintf(ip6tbuf, &mld->mld_addr),
                       ifp, if_name(ifp));
                   return (0);
           }
   
           /*
            * RFC3810 Section 6.2: MLD queries must originate from
            * a router's link-local address.
            */
           if (!IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) {
                   CTR3(KTR_MLD, "ignore v1 query src %s on ifp %p(%s)",
                       ip6_sprintf(ip6tbuf, &ip6->ip6_src),
                       ifp, if_name(ifp));
                   return (0);
           }
   
           /*
            * Do address field validation upfront before we accept
            * the query.
            */
           if (IN6_IS_ADDR_UNSPECIFIED(&mld->mld_addr)) {
                   /*
                    * MLDv1 General Query.
                    * If this was not sent to the all-nodes group, ignore it.
                    */
                   struct in6_addr          dst;
   
                   dst = ip6->ip6_dst;
                   in6_clearscope(&dst);
                   if (!IN6_ARE_ADDR_EQUAL(&dst, &in6addr_linklocal_allnodes))
                           return (EINVAL);
                   is_general_query = 1;
           } else {
                   /*
                    * Embed scope ID of receiving interface in MLD query for
                    * lookup whilst we don't hold other locks.
                    */
                   in6_setscope(&mld->mld_addr, ifp, NULL);
           }
   
           IN6_MULTI_LIST_LOCK();
           MLD_LOCK();
   
           /*
            * Switch to MLDv1 host compatibility mode.
            */
           mli = MLD_IFINFO(ifp);
           KASSERT(mli != NULL, ("%s: no mld_ifsoftc for ifp %p", __func__, ifp));
           mld_set_version(mli, MLD_VERSION_1);
   
           timer = (ntohs(mld->mld_maxdelay) * MLD_FASTHZ) / MLD_TIMER_SCALE;
           if (timer == 0)
                   timer = 1;
   
           if (is_general_query) {
                   /*
                    * For each reporting group joined on this
                    * interface, kick the report timer.
                    */
                   CTR2(KTR_MLD, "process v1 general query on ifp %p(%s)",
                            ifp, if_name(ifp));
                   CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                           inm = in6m_ifmultiaddr_get_inm(ifma);
                           if (inm == NULL)
                                   continue;
                           mld_v1_update_group(inm, timer);
                   }
           } else {
                   /*
                    * MLDv1 Group-Specific Query.
                    * If this is a group-specific MLDv1 query, we need only
                    * look up the single group to process it.
                    */
                   inm = in6m_lookup_locked(ifp, &mld->mld_addr);
                   if (inm != NULL) {
                           CTR3(KTR_MLD, "process v1 query %s on ifp %p(%s)",
                               ip6_sprintf(ip6tbuf, &mld->mld_addr),
                               ifp, if_name(ifp));
                           mld_v1_update_group(inm, timer);
                   }
                   /* XXX Clear embedded scope ID as userland won't expect it. */
                   in6_clearscope(&mld->mld_addr);
           }
   
           MLD_UNLOCK();
           IN6_MULTI_LIST_UNLOCK();
   
           return (0);
   }
   
   /*
    * Update the report timer on a group in response to an MLDv1 query.
    *
    * If we are becoming the reporting member for this group, start the timer.
    * If we already are the reporting member for this group, and timer is
    * below the threshold, reset it.
    *
    * We may be updating the group for the first time since we switched
    * to MLDv2. If we are, then we must clear any recorded source lists,
    * and transition to REPORTING state; the group timer is overloaded
    * for group and group-source query responses. 
    *
    * Unlike MLDv2, the delay per group should be jittered
    * to avoid bursts of MLDv1 reports.
    */
   static void
   mld_v1_update_group(struct in6_multi *inm, const int timer)
   {
   #ifdef KTR
           char                     ip6tbuf[INET6_ADDRSTRLEN];
   #endif
   
           CTR4(KTR_MLD, "%s: %s/%s timer=%d", __func__,
               ip6_sprintf(ip6tbuf, &inm->in6m_addr),
               if_name(inm->in6m_ifp), timer);
   
           IN6_MULTI_LIST_LOCK_ASSERT();
   
           switch (inm->in6m_state) {
           case MLD_NOT_MEMBER:
           case MLD_SILENT_MEMBER:
                   break;
           case MLD_REPORTING_MEMBER:
                   if (inm->in6m_timer != 0 &&
                       inm->in6m_timer <= timer) {
                           CTR1(KTR_MLD, "%s: REPORTING and timer running, "
                               "skipping.", __func__);
                           break;
                   }
                   /* FALLTHROUGH */
           case MLD_SG_QUERY_PENDING_MEMBER:
           case MLD_G_QUERY_PENDING_MEMBER:
           case MLD_IDLE_MEMBER:
           case MLD_LAZY_MEMBER:
           case MLD_AWAKENING_MEMBER:
                   CTR1(KTR_MLD, "%s: ->REPORTING", __func__);
                   inm->in6m_state = MLD_REPORTING_MEMBER;
                   inm->in6m_timer = MLD_RANDOM_DELAY(timer);
                   V_current_state_timers_running6 = 1;
                   break;
           case MLD_SLEEPING_MEMBER:
                   CTR1(KTR_MLD, "%s: ->AWAKENING", __func__);
                   inm->in6m_state = MLD_AWAKENING_MEMBER;
                   break;
           case MLD_LEAVING_MEMBER:
                   break;
           }
   }
   
   /*
    * Process a received MLDv2 general, group-specific or
    * group-and-source-specific query.
    *
    * Assumes that mld points to a struct mldv2_query which is stored in
    * contiguous memory.
    *
    * Return 0 if successful, otherwise an appropriate error code is returned.
    */
   static int
   mld_v2_input_query(struct ifnet *ifp, const struct ip6_hdr *ip6,
       struct mbuf *m, struct mldv2_query *mld, const int off, const int icmp6len)
   {
           struct mld_ifsoftc      *mli;
           struct in6_multi        *inm;
           uint32_t                 maxdelay, nsrc, qqi;
           int                      is_general_query;
           uint16_t                 timer;
           uint8_t                  qrv;
   #ifdef KTR
           char                     ip6tbuf[INET6_ADDRSTRLEN];
   #endif
   
           NET_EPOCH_ASSERT();
   
           if (!mld_v2enable) {
                   CTR3(KTR_MLD, "ignore v2 query src %s on ifp %p(%s)",
                       ip6_sprintf(ip6tbuf, &ip6->ip6_src),
                       ifp, if_name(ifp));
                   return (0);
           }
   
           /*
            * RFC3810 Section 6.2: MLD queries must originate from
            * a router's link-local address.
            */
           if (!IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) {
                   CTR3(KTR_MLD, "ignore v1 query src %s on ifp %p(%s)",
                       ip6_sprintf(ip6tbuf, &ip6->ip6_src),
                       ifp, if_name(ifp));
                   return (0);
           }
   
           is_general_query = 0;
   
           CTR2(KTR_MLD, "input v2 query on ifp %p(%s)", ifp, if_name(ifp));
   
           maxdelay = ntohs(mld->mld_maxdelay);    /* in 1/10ths of a second */
           if (maxdelay >= 32768) {
                   maxdelay = (MLD_MRC_MANT(maxdelay) | 0x1000) <<
                              (MLD_MRC_EXP(maxdelay) + 3);
           }
           timer = (maxdelay * MLD_FASTHZ) / MLD_TIMER_SCALE;
           if (timer == 0)
                   timer = 1;
   
           qrv = MLD_QRV(mld->mld_misc);
           if (qrv < 2) {
                   CTR3(KTR_MLD, "%s: clamping qrv %d to %d", __func__,
                       qrv, MLD_RV_INIT);
                   qrv = MLD_RV_INIT;
           }
   
           qqi = mld->mld_qqi;
           if (qqi >= 128) {
                   qqi = MLD_QQIC_MANT(mld->mld_qqi) <<
                        (MLD_QQIC_EXP(mld->mld_qqi) + 3);
           }
   
           nsrc = ntohs(mld->mld_numsrc);
           if (nsrc > MLD_MAX_GS_SOURCES)
                   return (EMSGSIZE);
           if (icmp6len < sizeof(struct mldv2_query) +
               (nsrc * sizeof(struct in6_addr)))
                   return (EMSGSIZE);
   
           /*
            * Do further input validation upfront to avoid resetting timers
            * should we need to discard this query.
            */
           if (IN6_IS_ADDR_UNSPECIFIED(&mld->mld_addr)) {
                   /*
                    * A general query with a source list has undefined
                    * behaviour; discard it.
                    */
                   if (nsrc > 0)
                           return (EINVAL);
                   is_general_query = 1;
           } else {
                   /*
                    * Embed scope ID of receiving interface in MLD query for
                    * lookup whilst we don't hold other locks (due to KAME
                    * locking lameness). We own this mbuf chain just now.
                    */
                   in6_setscope(&mld->mld_addr, ifp, NULL);
           }
   
           IN6_MULTI_LIST_LOCK();
           MLD_LOCK();
   
           mli = MLD_IFINFO(ifp);
           KASSERT(mli != NULL, ("%s: no mld_ifsoftc for ifp %p", __func__, ifp));
   
           /*
            * Discard the v2 query if we're in Compatibility Mode.
            * The RFC is pretty clear that hosts need to stay in MLDv1 mode
            * until the Old Version Querier Present timer expires.
            */
           if (mli->mli_version != MLD_VERSION_2)
                   goto out_locked;
   
           mld_set_version(mli, MLD_VERSION_2);
           mli->mli_rv = qrv;
           mli->mli_qi = qqi;
           mli->mli_qri = maxdelay;
   
           CTR4(KTR_MLD, "%s: qrv %d qi %d maxdelay %d", __func__, qrv, qqi,
               maxdelay);
   
           if (is_general_query) {
                   /*
                    * MLDv2 General Query.
                    *
                    * Schedule a current-state report on this ifp for
                    * all groups, possibly containing source lists.
                    *
                    * If there is a pending General Query response
                    * scheduled earlier than the selected delay, do
                    * not schedule any other reports.
                    * Otherwise, reset the interface timer.
                    */
                   CTR2(KTR_MLD, "process v2 general query on ifp %p(%s)",
                       ifp, if_name(ifp));
                   if (mli->mli_v2_timer == 0 || mli->mli_v2_timer >= timer) {
                           mli->mli_v2_timer = MLD_RANDOM_DELAY(timer);
                           V_interface_timers_running6 = 1;
                   }
           } else {
                   /*
                    * MLDv2 Group-specific or Group-and-source-specific Query.
                    *
                    * Group-source-specific queries are throttled on
                    * a per-group basis to defeat denial-of-service attempts.
                    * Queries for groups we are not a member of on this
                    * link are simply ignored.
                    */
                   inm = in6m_lookup_locked(ifp, &mld->mld_addr);
                   if (inm == NULL)
                           goto out_locked;
                   if (nsrc > 0) {
                           if (!ratecheck(&inm->in6m_lastgsrtv,
                               &V_mld_gsrdelay)) {
                                   CTR1(KTR_MLD, "%s: GS query throttled.",
                                       __func__);
                                   goto out_locked;
                           }
                   }
                   CTR2(KTR_MLD, "process v2 group query on ifp %p(%s)",
                        ifp, if_name(ifp));
                   /*
                    * If there is a pending General Query response
                    * scheduled sooner than the selected delay, no
                    * further report need be scheduled.
                    * Otherwise, prepare to respond to the
                    * group-specific or group-and-source query.
                    */
                   if (mli->mli_v2_timer == 0 || mli->mli_v2_timer >= timer)
                           mld_v2_process_group_query(inm, mli, timer, m, mld, off);
   
                   /* XXX Clear embedded scope ID as userland won't expect it. */
                   in6_clearscope(&mld->mld_addr);
           }
   
   out_locked:
           MLD_UNLOCK();
           IN6_MULTI_LIST_UNLOCK();
   
           return (0);
   }
   
   /*
    * Process a received MLDv2 group-specific or group-and-source-specific
    * query.
    * Return <0 if any error occurred. Currently this is ignored.
    */
   static int
   mld_v2_process_group_query(struct in6_multi *inm, struct mld_ifsoftc *mli,
       int timer, struct mbuf *m0, struct mldv2_query *mld, const int off)
   {
           int                      retval;
           uint16_t                 nsrc;
   
           IN6_MULTI_LIST_LOCK_ASSERT();
           MLD_LOCK_ASSERT();
   
           retval = 0;
   
           switch (inm->in6m_state) {
           case MLD_NOT_MEMBER:
           case MLD_SILENT_MEMBER:
           case MLD_SLEEPING_MEMBER:
           case MLD_LAZY_MEMBER:
           case MLD_AWAKENING_MEMBER:
           case MLD_IDLE_MEMBER:
           case MLD_LEAVING_MEMBER:
                   return (retval);
                   break;
           case MLD_REPORTING_MEMBER:
           case MLD_G_QUERY_PENDING_MEMBER:
           case MLD_SG_QUERY_PENDING_MEMBER:
                   break;
           }
   
           nsrc = ntohs(mld->mld_numsrc);
   
           /* Length should be checked by calling function. */
           KASSERT((m0->m_flags & M_PKTHDR) == 0 ||
               m0->m_pkthdr.len >= off + sizeof(struct mldv2_query) +
               nsrc * sizeof(struct in6_addr),
               ("mldv2 packet is too short: (%d bytes < %zd bytes, m=%p)",
               m0->m_pkthdr.len, off + sizeof(struct mldv2_query) +
               nsrc * sizeof(struct in6_addr), m0));
   
           /*
            * Deal with group-specific queries upfront.
            * If any group query is already pending, purge any recorded
            * source-list state if it exists, and schedule a query response
            * for this group-specific query.
            */
          if (nsrc == 0) {
                  if (inm->in6m_state == MLD_G_QUERY_PENDING_MEMBER ||
                      inm->in6m_state == MLD_SG_QUERY_PENDING_MEMBER) {
                          in6m_clear_recorded(inm);
                          timer = min(inm->in6m_timer, timer);
                  }
                  inm->in6m_state = MLD_G_QUERY_PENDING_MEMBER;
                  inm->in6m_timer = MLD_RANDOM_DELAY(timer);
                  V_current_state_timers_running6 = 1;
                  return (retval);
          }
  
          /*
           * Deal with the case where a group-and-source-specific query has
           * been received but a group-specific query is already pending.
           */
          if (inm->in6m_state == MLD_G_QUERY_PENDING_MEMBER) {
                  timer = min(inm->in6m_timer, timer);
                  inm->in6m_timer = MLD_RANDOM_DELAY(timer);
                  V_current_state_timers_running6 = 1;
                  return (retval);
          }
  
          /*
           * Finally, deal with the case where a group-and-source-specific
           * query has been received, where a response to a previous g-s-r
           * query exists, or none exists.
           * In this case, we need to parse the source-list which the Querier
           * has provided us with and check if we have any source list filter
           * entries at T1 for these sources. If we do not, there is no need
           * schedule a report and the query may be dropped.
           * If we do, we must record them and schedule a current-state
           * report for those sources.
           */
          if (inm->in6m_nsrc > 0) {
                  struct in6_addr          srcaddr;
                  int                      i, nrecorded;
                  int                      soff;
  
                  soff = off + sizeof(struct mldv2_query);
                  nrecorded = 0;
                  for (i = 0; i < nsrc; i++) {
                          m_copydata(m0, soff, sizeof(struct in6_addr),
                              (caddr_t)&srcaddr);
                          retval = in6m_record_source(inm, &srcaddr);
                          if (retval < 0)
                                  break;
                          nrecorded += retval;
                          soff += sizeof(struct in6_addr);
                  }
                  if (nrecorded > 0) {
                          CTR1(KTR_MLD,
                              "%s: schedule response to SG query", __func__);
                          inm->in6m_state = MLD_SG_QUERY_PENDING_MEMBER;
                          inm->in6m_timer = MLD_RANDOM_DELAY(timer);
                          V_current_state_timers_running6 = 1;
                  }
          }
  
          return (retval);
  }
  
  /*
   * Process a received MLDv1 host membership report.
   * Assumes mld points to mld_hdr in pulled up mbuf chain.
   *
   * NOTE: Can't be fully const correct as we temporarily embed scope ID in
   * mld_addr. This is OK as we own the mbuf chain.
   */
  static int
  mld_v1_input_report(struct ifnet *ifp, const struct ip6_hdr *ip6,
      /*const*/ struct mld_hdr *mld)
  {
          struct in6_addr          src, dst;
          struct in6_ifaddr       *ia;
          struct in6_multi        *inm;
  #ifdef KTR
          char                     ip6tbuf[INET6_ADDRSTRLEN];
  #endif
  
          NET_EPOCH_ASSERT();
  
          if (!mld_v1enable) {
                  CTR3(KTR_MLD, "ignore v1 report %s on ifp %p(%s)",
                      ip6_sprintf(ip6tbuf, &mld->mld_addr),
                      ifp, if_name(ifp));
                  return (0);
          }
  
          if (ifp->if_flags & IFF_LOOPBACK)
                  return (0);
  
          /*
           * MLDv1 reports must originate from a host's link-local address,
           * or the unspecified address (when booting).
           */
          src = ip6->ip6_src;
          in6_clearscope(&src);
          if (!IN6_IS_SCOPE_LINKLOCAL(&src) && !IN6_IS_ADDR_UNSPECIFIED(&src)) {
                  CTR3(KTR_MLD, "ignore v1 query src %s on ifp %p(%s)",
                      ip6_sprintf(ip6tbuf, &ip6->ip6_src),
                      ifp, if_name(ifp));
                  return (EINVAL);
          }
  
          /*
           * RFC2710 Section 4: MLDv1 reports must pertain to a multicast
           * group, and must be directed to the group itself.
           */
          dst = ip6->ip6_dst;
          in6_clearscope(&dst);
          if (!IN6_IS_ADDR_MULTICAST(&mld->mld_addr) ||
              !IN6_ARE_ADDR_EQUAL(&mld->mld_addr, &dst)) {
                  CTR3(KTR_MLD, "ignore v1 query dst %s on ifp %p(%s)",
                      ip6_sprintf(ip6tbuf, &ip6->ip6_dst),
                      ifp, if_name(ifp));
                  return (EINVAL);
          }
  
          /*
           * Make sure we don't hear our own membership report, as fast
           * leave requires knowing that we are the only member of a
           * group. Assume we used the link-local address if available,
           * otherwise look for ::.
           *
           * XXX Note that scope ID comparison is needed for the address
           * returned by in6ifa_ifpforlinklocal(), but SHOULD NOT be
           * performed for the on-wire address.
           */
          ia = in6ifa_ifpforlinklocal(ifp, IN6_IFF_NOTREADY|IN6_IFF_ANYCAST);
          if ((ia && IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, IA6_IN6(ia))) ||
              (ia == NULL && IN6_IS_ADDR_UNSPECIFIED(&src))) {
                  if (ia != NULL)
                          ifa_free(&ia->ia_ifa);
                  return (0);
          }
          if (ia != NULL)
                  ifa_free(&ia->ia_ifa);
  
          CTR3(KTR_MLD, "process v1 report %s on ifp %p(%s)",
              ip6_sprintf(ip6tbuf, &mld->mld_addr), ifp, if_name(ifp));
  
          /*
           * Embed scope ID of receiving interface in MLD query for lookup
           * whilst we don't hold other locks (due to KAME locking lameness).
           */
          if (!IN6_IS_ADDR_UNSPECIFIED(&mld->mld_addr))
                  in6_setscope(&mld->mld_addr, ifp, NULL);
  
          IN6_MULTI_LIST_LOCK();
          MLD_LOCK();
  
          /*
           * MLDv1 report suppression.
           * If we are a member of this group, and our membership should be
           * reported, and our group timer is pending or about to be reset,
           * stop our group timer by transitioning to the 'lazy' state.
           */
          inm = in6m_lookup_locked(ifp, &mld->mld_addr);
          if (inm != NULL) {
                  struct mld_ifsoftc *mli;
  
                  mli = inm->in6m_mli;
                  KASSERT(mli != NULL,
                      ("%s: no mli for ifp %p", __func__, ifp));
  
                  /*
                   * If we are in MLDv2 host mode, do not allow the
                   * other host's MLDv1 report to suppress our reports.
                   */
                  if (mli->mli_version == MLD_VERSION_2)
                          goto out_locked;
  
                  inm->in6m_timer = 0;
  
                  switch (inm->in6m_state) {
                  case MLD_NOT_MEMBER:
                  case MLD_SILENT_MEMBER:
                  case MLD_SLEEPING_MEMBER:
                          break;
                  case MLD_REPORTING_MEMBER:
                  case MLD_IDLE_MEMBER:
                  case MLD_AWAKENING_MEMBER:
                          CTR3(KTR_MLD,
                              "report suppressed for %s on ifp %p(%s)",
                              ip6_sprintf(ip6tbuf, &mld->mld_addr),
                              ifp, if_name(ifp));
                  case MLD_LAZY_MEMBER:
                          inm->in6m_state = MLD_LAZY_MEMBER;
                          break;
                  case MLD_G_QUERY_PENDING_MEMBER:
                  case MLD_SG_QUERY_PENDING_MEMBER:
                  case MLD_LEAVING_MEMBER:
                          break;
                  }
          }
  
  out_locked:
          MLD_UNLOCK();
          IN6_MULTI_LIST_UNLOCK();
  
          /* XXX Clear embedded scope ID as userland won't expect it. */
          in6_clearscope(&mld->mld_addr);
  
          return (0);
  }
  
  /*
   * MLD input path.
   *
   * Assume query messages which fit in a single ICMPv6 message header
   * have been pulled up.
   * Assume that userland will want to see the message, even if it
   * otherwise fails kernel input validation; do not free it.
   * Pullup may however free the mbuf chain m if it fails.
   *
   * Return IPPROTO_DONE if we freed m. Otherwise, return 0.
   */
  int
  mld_input(struct mbuf **mp, int off, int icmp6len)
  {
          struct ifnet    *ifp;
          struct ip6_hdr  *ip6;
          struct mbuf     *m;
          struct mld_hdr  *mld;
          int              mldlen;
  
          m = *mp;
          CTR3(KTR_MLD, "%s: called w/mbuf (%p,%d)", __func__, m, off);
  
          ifp = m->m_pkthdr.rcvif;
  
          /* Pullup to appropriate size. */
          if (m->m_len < off + sizeof(*mld)) {
                  m = m_pullup(m, off + sizeof(*mld));
                  if (m == NULL) {
                          ICMP6STAT_INC(icp6s_badlen);
                          return (IPPROTO_DONE);
                  }
          }
          mld = (struct mld_hdr *)(mtod(m, uint8_t *) + off);
          if (mld->mld_type == MLD_LISTENER_QUERY &&
              icmp6len >= sizeof(struct mldv2_query)) {
                  mldlen = sizeof(struct mldv2_query);
          } else {
                  mldlen = sizeof(struct mld_hdr);
          }
          if (m->m_len < off + mldlen) {
                  m = m_pullup(m, off + mldlen);
                  if (m == NULL) {
                          ICMP6STAT_INC(icp6s_badlen);
                          return (IPPROTO_DONE);
                  }
          }
          *mp = m;
          ip6 = mtod(m, struct ip6_hdr *);
          mld = (struct mld_hdr *)(mtod(m, uint8_t *) + off);
  
          /*
           * Userland needs to see all of this traffic for implementing
           * the endpoint discovery portion of multicast routing.
           */
          switch (mld->mld_type) {
          case MLD_LISTENER_QUERY:
                  icmp6_ifstat_inc(ifp, ifs6_in_mldquery);
                  if (icmp6len == sizeof(struct mld_hdr)) {
                          if (mld_v1_input_query(ifp, ip6, mld) != 0)
                                  return (0);
                  } else if (icmp6len >= sizeof(struct mldv2_query)) {
                          if (mld_v2_input_query(ifp, ip6, m,
                              (struct mldv2_query *)mld, off, icmp6len) != 0)
                                  return (0);
                  }
                  break;
          case MLD_LISTENER_REPORT:
                  icmp6_ifstat_inc(ifp, ifs6_in_mldreport);
                  if (mld_v1_input_report(ifp, ip6, mld) != 0)
                          return (0);
                  break;
          case MLDV2_LISTENER_REPORT:
                  icmp6_ifstat_inc(ifp, ifs6_in_mldreport);
                  break;
          case MLD_LISTENER_DONE:
                  icmp6_ifstat_inc(ifp, ifs6_in_mlddone);
                  break;
          default:
                  break;
          }
  
          return (0);
  }
  
  /*
   * Fast timeout handler (global).
   * VIMAGE: Timeout handlers are expected to service all vimages.
   */
  static struct callout mldfast_callout;
  static void
  mld_fasttimo(void *arg __unused)
  {
          struct epoch_tracker et;
          struct in6_multi_head inmh;
          VNET_ITERATOR_DECL(vnet_iter);
  
          SLIST_INIT(&inmh);
  
          NET_EPOCH_ENTER(et);
          VNET_LIST_RLOCK_NOSLEEP();
          VNET_FOREACH(vnet_iter) {
                  CURVNET_SET(vnet_iter);
                  mld_fasttimo_vnet(&inmh);
                  CURVNET_RESTORE();
          }
          VNET_LIST_RUNLOCK_NOSLEEP();
          NET_EPOCH_EXIT(et);
          in6m_release_list_deferred(&inmh);
  
          callout_reset(&mldfast_callout, hz / MLD_FASTHZ, mld_fasttimo, NULL);
  }
  
  /*
   * Fast timeout handler (per-vnet).
   *
   * VIMAGE: Assume caller has set up our curvnet.
   */
  static void
  mld_fasttimo_vnet(struct in6_multi_head *inmh)
  {
          struct mbufq             scq;   /* State-change packets */
          struct mbufq             qrq;   /* Query response packets */
          struct ifnet            *ifp;
          struct mld_ifsoftc      *mli;
          struct ifmultiaddr      *ifma;
          struct in6_multi        *inm;
          int                      uri_fasthz;
  
          uri_fasthz = 0;
  
          /*
           * Quick check to see if any work needs to be done, in order to
           * minimize the overhead of fasttimo processing.
           * SMPng: XXX Unlocked reads.
           */
          if (!V_current_state_timers_running6 &&
              !V_interface_timers_running6 &&
              !V_state_change_timers_running6)
                  return;
  
          IN6_MULTI_LIST_LOCK();
          MLD_LOCK();
  
          /*
           * MLDv2 General Query response timer processing.
           */
          if (V_interface_timers_running6) {
                  CTR1(KTR_MLD, "%s: interface timers running", __func__);
  
                  V_interface_timers_running6 = 0;
                  LIST_FOREACH(mli, &V_mli_head, mli_link) {
                          if (mli->mli_v2_timer == 0) {
                                  /* Do nothing. */
                          } else if (--mli->mli_v2_timer == 0) {
                                  mld_v2_dispatch_general_query(mli);
                          } else {
                                  V_interface_timers_running6 = 1;
                          }
                  }
          }
  
          if (!V_current_state_timers_running6 &&
              !V_state_change_timers_running6)
                  goto out_locked;
  
          V_current_state_timers_running6 = 0;
          V_state_change_timers_running6 = 0;
  
          CTR1(KTR_MLD, "%s: state change timers running", __func__);
  
          /*
           * MLD host report and state-change timer processing.
           * Note: Processing a v2 group timer may remove a node.
           */
          LIST_FOREACH(mli, &V_mli_head, mli_link) {
                  ifp = mli->mli_ifp;
  
                  if (mli->mli_version == MLD_VERSION_2) {
                          uri_fasthz = MLD_RANDOM_DELAY(mli->mli_uri *
                              MLD_FASTHZ);
                          mbufq_init(&qrq, MLD_MAX_G_GS_PACKETS);
                          mbufq_init(&scq, MLD_MAX_STATE_CHANGE_PACKETS);
                  }
  
                  IF_ADDR_WLOCK(ifp);
                  CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                          inm = in6m_ifmultiaddr_get_inm(ifma);
                          if (inm == NULL)
                                  continue;
                          switch (mli->mli_version) {
                          case MLD_VERSION_1:
                                  mld_v1_process_group_timer(inmh, inm);
                                  break;
                          case MLD_VERSION_2:
                                  mld_v2_process_group_timers(inmh, &qrq,
                                      &scq, inm, uri_fasthz);
                                  break;
                          }
                  }
                  IF_ADDR_WUNLOCK(ifp);
  
                  switch (mli->mli_version) {
                  case MLD_VERSION_1:
                          /*
                           * Transmit reports for this lifecycle.  This
                           * is done while not holding IF_ADDR_LOCK
                           * since this can call
                           * in6ifa_ifpforlinklocal() which locks
                           * IF_ADDR_LOCK internally as well as
                           * ip6_output() to transmit a packet.
                           */
                          while ((inm = SLIST_FIRST(inmh)) != NULL) {
                                  SLIST_REMOVE_HEAD(inmh, in6m_defer);
                                  (void)mld_v1_transmit_report(inm,
                                      MLD_LISTENER_REPORT);
                          }
                          break;
                  case MLD_VERSION_2:
                          mld_dispatch_queue(&qrq, 0);
                          mld_dispatch_queue(&scq, 0);
                          break;
                  }
          }
  
  out_locked:
          MLD_UNLOCK();
          IN6_MULTI_LIST_UNLOCK();
  }
  
  /*
   * Update host report group timer.
   * Will update the global pending timer flags.
   */
  static void
  mld_v1_process_group_timer(struct in6_multi_head *inmh, struct in6_multi *inm)
  {
          int report_timer_expired;
  
          IN6_MULTI_LIST_LOCK_ASSERT();
          MLD_LOCK_ASSERT();
  
          if (inm->in6m_timer == 0) {
                  report_timer_expired = 0;
          } else if (--inm->in6m_timer == 0) {
                  report_timer_expired = 1;
          } else {
                  V_current_state_timers_running6 = 1;
                  return;
          }
  
          switch (inm->in6m_state) {
          case MLD_NOT_MEMBER:
          case MLD_SILENT_MEMBER:
          case MLD_IDLE_MEMBER:
          case MLD_LAZY_MEMBER:
          case MLD_SLEEPING_MEMBER:
          case MLD_AWAKENING_MEMBER:
                  break;
          case MLD_REPORTING_MEMBER:
                  if (report_timer_expired) {
                          inm->in6m_state = MLD_IDLE_MEMBER;
                          SLIST_INSERT_HEAD(inmh, inm, in6m_defer);
                  }
                  break;
          case MLD_G_QUERY_PENDING_MEMBER:
          case MLD_SG_QUERY_PENDING_MEMBER:
          case MLD_LEAVING_MEMBER:
                  break;
          }
  }
  
  /*
   * Update a group's timers for MLDv2.
   * Will update the global pending timer flags.
   * Note: Unlocked read from mli.
   */
  static void
  mld_v2_process_group_timers(struct in6_multi_head *inmh,
      struct mbufq *qrq, struct mbufq *scq,
      struct in6_multi *inm, const int uri_fasthz)
  {
          int query_response_timer_expired;
          int state_change_retransmit_timer_expired;
  #ifdef KTR
          char ip6tbuf[INET6_ADDRSTRLEN];
  #endif
  
          IN6_MULTI_LIST_LOCK_ASSERT();
          MLD_LOCK_ASSERT();
  
          query_response_timer_expired = 0;
          state_change_retransmit_timer_expired = 0;
  
          /*
           * During a transition from compatibility mode back to MLDv2,
           * a group record in REPORTING state may still have its group
           * timer active. This is a no-op in this function; it is easier
           * to deal with it here than to complicate the slow-timeout path.
           */
          if (inm->in6m_timer == 0) {
                  query_response_timer_expired = 0;
          } else if (--inm->in6m_timer == 0) {
                  query_response_timer_expired = 1;
          } else {
                  V_current_state_timers_running6 = 1;
          }
  
          if (inm->in6m_sctimer == 0) {
                  state_change_retransmit_timer_expired = 0;
          } else if (--inm->in6m_sctimer == 0) {
                  state_change_retransmit_timer_expired = 1;
          } else {
                  V_state_change_timers_running6 = 1;
          }
  
          /* We are in fasttimo, so be quick about it. */
          if (!state_change_retransmit_timer_expired &&
              !query_response_timer_expired)
                  return;
  
          switch (inm->in6m_state) {
          case MLD_NOT_MEMBER:
          case MLD_SILENT_MEMBER:
          case MLD_SLEEPING_MEMBER:
          case MLD_LAZY_MEMBER:
          case MLD_AWAKENING_MEMBER:
          case MLD_IDLE_MEMBER:
                  break;
          case MLD_G_QUERY_PENDING_MEMBER:
          case MLD_SG_QUERY_PENDING_MEMBER:
                  /*
                   * Respond to a previously pending Group-Specific
                   * or Group-and-Source-Specific query by enqueueing
                   * the appropriate Current-State report for
                   * immediate transmission.
                   */
                  if (query_response_timer_expired) {
                          int retval __unused;
  
                          retval = mld_v2_enqueue_group_record(qrq, inm, 0, 1,
                              (inm->in6m_state == MLD_SG_QUERY_PENDING_MEMBER),
                              0);
                          CTR2(KTR_MLD, "%s: enqueue record = %d",
                              __func__, retval);
                          inm->in6m_state = MLD_REPORTING_MEMBER;
                          in6m_clear_recorded(inm);
                  }
                  /* FALLTHROUGH */
          case MLD_REPORTING_MEMBER:
          case MLD_LEAVING_MEMBER:
                  if (state_change_retransmit_timer_expired) {
                          /*
                           * State-change retransmission timer fired.
                           * If there are any further pending retransmissions,
                           * set the global pending state-change flag, and
                           * reset the timer.
                           */
                          if (--inm->in6m_scrv > 0) {
                                  inm->in6m_sctimer = uri_fasthz;
                                  V_state_change_timers_running6 = 1;
                          }
                          /*
                           * Retransmit the previously computed state-change
                           * report. If there are no further pending
                           * retransmissions, the mbuf queue will be consumed.
                           * Update T0 state to T1 as we have now sent
                           * a state-change.
                           */
                          (void)mld_v2_merge_state_changes(inm, scq);
  
                          in6m_commit(inm);
                          CTR3(KTR_MLD, "%s: T1 -> T0 for %s/%s", __func__,
                              ip6_sprintf(ip6tbuf, &inm->in6m_addr),
                              if_name(inm->in6m_ifp));
  
                          /*
                           * If we are leaving the group for good, make sure
                           * we release MLD's reference to it.
                           * This release must be deferred using a SLIST,
                           * as we are called from a loop which traverses
                           * the in_ifmultiaddr TAILQ.
                           */
                          if (inm->in6m_state == MLD_LEAVING_MEMBER &&
                              inm->in6m_scrv == 0) {
                                  inm->in6m_state = MLD_NOT_MEMBER;
                                  in6m_disconnect_locked(inmh, inm);
                                  in6m_rele_locked(inmh, inm);
                          }
                  }
                  break;
          }
  }
  
  /*
   * Switch to a different version on the given interface,
   * as per Section 9.12.
   */
  static void
  mld_set_version(struct mld_ifsoftc *mli, const int version)
  {
          int old_version_timer;
  
          MLD_LOCK_ASSERT();
  
          CTR4(KTR_MLD, "%s: switching to v%d on ifp %p(%s)", __func__,
              version, mli->mli_ifp, if_name(mli->mli_ifp));
  
          if (version == MLD_VERSION_1) {
                  /*
                   * Compute the "Older Version Querier Present" timer as per
                   * Section 9.12.
                   */
                  old_version_timer = (mli->mli_rv * mli->mli_qi) + mli->mli_qri;
                  old_version_timer *= MLD_SLOWHZ;
                  mli->mli_v1_timer = old_version_timer;
          }
  
          if (mli->mli_v1_timer > 0 && mli->mli_version != MLD_VERSION_1) {
                  mli->mli_version = MLD_VERSION_1;
                  mld_v2_cancel_link_timers(mli);
          }
  }
  
  /*
   * Cancel pending MLDv2 timers for the given link and all groups
   * joined on it; state-change, general-query, and group-query timers.
   */
  static void
  mld_v2_cancel_link_timers(struct mld_ifsoftc *mli)
  {
          struct epoch_tracker     et;
          struct in6_multi_head    inmh;
          struct ifmultiaddr      *ifma;
          struct ifnet            *ifp;
          struct in6_multi        *inm;
  
          CTR3(KTR_MLD, "%s: cancel v2 timers on ifp %p(%s)", __func__,
              mli->mli_ifp, if_name(mli->mli_ifp));
  
          SLIST_INIT(&inmh);
          IN6_MULTI_LIST_LOCK_ASSERT();
          MLD_LOCK_ASSERT();
  
          /*
           * Fast-track this potentially expensive operation
           * by checking all the global 'timer pending' flags.
           */
          if (!V_interface_timers_running6 &&
              !V_state_change_timers_running6 &&
              !V_current_state_timers_running6)
                  return;
  
          mli->mli_v2_timer = 0;
  
          ifp = mli->mli_ifp;
  
          IF_ADDR_WLOCK(ifp);
          NET_EPOCH_ENTER(et);
          CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                  inm = in6m_ifmultiaddr_get_inm(ifma);
                  if (inm == NULL)
                          continue;
                  switch (inm->in6m_state) {
                  case MLD_NOT_MEMBER:
                  case MLD_SILENT_MEMBER:
                  case MLD_IDLE_MEMBER:
                  case MLD_LAZY_MEMBER:
                  case MLD_SLEEPING_MEMBER:
                  case MLD_AWAKENING_MEMBER:
                          break;
                  case MLD_LEAVING_MEMBER:
                          /*
                           * If we are leaving the group and switching
                           * version, we need to release the final
                           * reference held for issuing the INCLUDE {}.
                           */
                          if (inm->in6m_refcount == 1)
                                  in6m_disconnect_locked(&inmh, inm);
                          in6m_rele_locked(&inmh, inm);
                          /* FALLTHROUGH */
                  case MLD_G_QUERY_PENDING_MEMBER:
                  case MLD_SG_QUERY_PENDING_MEMBER:
                          in6m_clear_recorded(inm);
                          /* FALLTHROUGH */
                  case MLD_REPORTING_MEMBER:
                          inm->in6m_sctimer = 0;
                          inm->in6m_timer = 0;
                          inm->in6m_state = MLD_REPORTING_MEMBER;
                          /*
                           * Free any pending MLDv2 state-change records.
                           */
                          mbufq_drain(&inm->in6m_scq);
                          break;
                  }
          }
          NET_EPOCH_EXIT(et);
          IF_ADDR_WUNLOCK(ifp);
          in6m_release_list_deferred(&inmh);
  }
  
  /*
   * Global slowtimo handler.
   * VIMAGE: Timeout handlers are expected to service all vimages.
   */
  static struct callout mldslow_callout;
  static void
  mld_slowtimo(void *arg __unused)
  {
          VNET_ITERATOR_DECL(vnet_iter);
  
          VNET_LIST_RLOCK_NOSLEEP();
          VNET_FOREACH(vnet_iter) {
                  CURVNET_SET(vnet_iter);
                  mld_slowtimo_vnet();
                  CURVNET_RESTORE();
          }
          VNET_LIST_RUNLOCK_NOSLEEP();
  
          callout_reset(&mldslow_callout, hz / MLD_SLOWHZ, mld_slowtimo, NULL);
  }
  
  /*
   * Per-vnet slowtimo handler.
   */
  static void
  mld_slowtimo_vnet(void)
  {
          struct mld_ifsoftc *mli;
  
          MLD_LOCK();
  
          LIST_FOREACH(mli, &V_mli_head, mli_link) {
                  mld_v1_process_querier_timers(mli);
          }
  
          MLD_UNLOCK();
  }
  
  /*
   * Update the Older Version Querier Present timers for a link.
   * See Section 9.12 of RFC 3810.
   */
  static void
  mld_v1_process_querier_timers(struct mld_ifsoftc *mli)
  {
  
          MLD_LOCK_ASSERT();
  
          if (mli->mli_version != MLD_VERSION_2 && --mli->mli_v1_timer == 0) {
                  /*
                   * MLDv1 Querier Present timer expired; revert to MLDv2.
                   */
                  CTR5(KTR_MLD,
                      "%s: transition from v%d -> v%d on %p(%s)",
                      __func__, mli->mli_version, MLD_VERSION_2,
                      mli->mli_ifp, if_name(mli->mli_ifp));
                  mli->mli_version = MLD_VERSION_2;
          }
  }
  
  /*
   * Transmit an MLDv1 report immediately.
   */
  static int
  mld_v1_transmit_report(struct in6_multi *in6m, const int type)
  {
          struct ifnet            *ifp;
          struct in6_ifaddr       *ia;
          struct ip6_hdr          *ip6;
          struct mbuf             *mh, *md;
          struct mld_hdr          *mld;
  
          NET_EPOCH_ASSERT();
          IN6_MULTI_LIST_LOCK_ASSERT();
          MLD_LOCK_ASSERT();
  
          ifp = in6m->in6m_ifp;
          /* in process of being freed */
          if (ifp == NULL)
                  return (0);
          ia = in6ifa_ifpforlinklocal(ifp, IN6_IFF_NOTREADY|IN6_IFF_ANYCAST);
          /* ia may be NULL if link-local address is tentative. */
  
          mh = m_gethdr(M_NOWAIT, MT_DATA);
          if (mh == NULL) {
                  if (ia != NULL)
                          ifa_free(&ia->ia_ifa);
                  return (ENOMEM);
          }
          md = m_get(M_NOWAIT, MT_DATA);
          if (md == NULL) {
                  m_free(mh);
                  if (ia != NULL)
                          ifa_free(&ia->ia_ifa);
                  return (ENOMEM);
          }
          mh->m_next = md;
  
          /*
           * FUTURE: Consider increasing alignment by ETHER_HDR_LEN, so
           * that ether_output() does not need to allocate another mbuf
           * for the header in the most common case.
           */
          M_ALIGN(mh, sizeof(struct ip6_hdr));
          mh->m_pkthdr.len = sizeof(struct ip6_hdr) + sizeof(struct mld_hdr);
          mh->m_len = sizeof(struct ip6_hdr);
  
          ip6 = mtod(mh, struct ip6_hdr *);
          ip6->ip6_flow = 0;
          ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
          ip6->ip6_vfc |= IPV6_VERSION;
          ip6->ip6_nxt = IPPROTO_ICMPV6;
          ip6->ip6_src = ia ? ia->ia_addr.sin6_addr : in6addr_any;
          ip6->ip6_dst = in6m->in6m_addr;
  
          md->m_len = sizeof(struct mld_hdr);
          mld = mtod(md, struct mld_hdr *);
          mld->mld_type = type;
          mld->mld_code = 0;
          mld->mld_cksum = 0;
          mld->mld_maxdelay = 0;
          mld->mld_reserved = 0;
          mld->mld_addr = in6m->in6m_addr;
          in6_clearscope(&mld->mld_addr);
          mld->mld_cksum = in6_cksum(mh, IPPROTO_ICMPV6,
              sizeof(struct ip6_hdr), sizeof(struct mld_hdr));
  
          mld_save_context(mh, ifp);
          mh->m_flags |= M_MLDV1;
  
          mld_dispatch_packet(mh);
  
          if (ia != NULL)
                  ifa_free(&ia->ia_ifa);
          return (0);
  }
  
  /*
   * Process a state change from the upper layer for the given IPv6 group.
   *
   * Each socket holds a reference on the in_multi in its own ip_moptions.
   * The socket layer will have made the necessary updates to.the group
   * state, it is now up to MLD to issue a state change report if there
   * has been any change between T0 (when the last state-change was issued)
   * and T1 (now).
   *
   * We use the MLDv2 state machine at group level. The MLd module
   * however makes the decision as to which MLD protocol version to speak.
   * A state change *from* INCLUDE {} always means an initial join.
   * A state change *to* INCLUDE {} always means a final leave.
   *
   * If delay is non-zero, and the state change is an initial multicast
   * join, the state change report will be delayed by 'delay' ticks
   * in units of MLD_FASTHZ if MLDv1 is active on the link; otherwise
   * the initial MLDv2 state change report will be delayed by whichever
   * is sooner, a pending state-change timer or delay itself.
   *
   * VIMAGE: curvnet should have been set by caller, as this routine
   * is called from the socket option handlers.
   */
  int
  mld_change_state(struct in6_multi *inm, const int delay)
  {
          struct mld_ifsoftc *mli;
          struct ifnet *ifp;
          int error;
  
          IN6_MULTI_LIST_LOCK_ASSERT();
  
          error = 0;
  
          /*
           * Check if the in6_multi has already been disconnected.
           */
          if (inm->in6m_ifp == NULL) {
                  CTR1(KTR_MLD, "%s: inm is disconnected", __func__);
                  return (0);
          }
  
          /*
           * Try to detect if the upper layer just asked us to change state
           * for an interface which has now gone away.
           */
          KASSERT(inm->in6m_ifma != NULL, ("%s: no ifma", __func__));
          ifp = inm->in6m_ifma->ifma_ifp;
          if (ifp == NULL)
                  return (0);
          /*
           * Sanity check that netinet6's notion of ifp is the
           * same as net's.
           */
          KASSERT(inm->in6m_ifp == ifp, ("%s: bad ifp", __func__));
  
          MLD_LOCK();
          mli = MLD_IFINFO(ifp);
          KASSERT(mli != NULL, ("%s: no mld_ifsoftc for ifp %p", __func__, ifp));
  
          /*
           * If we detect a state transition to or from MCAST_UNDEFINED
           * for this group, then we are starting or finishing an MLD
           * life cycle for this group.
           */
          if (inm->in6m_st[1].iss_fmode != inm->in6m_st[0].iss_fmode) {
                  CTR3(KTR_MLD, "%s: inm transition %d -> %d", __func__,
                      inm->in6m_st[0].iss_fmode, inm->in6m_st[1].iss_fmode);
                  if (inm->in6m_st[0].iss_fmode == MCAST_UNDEFINED) {
                          CTR1(KTR_MLD, "%s: initial join", __func__);
                          error = mld_initial_join(inm, mli, delay);
                          goto out_locked;
                  } else if (inm->in6m_st[1].iss_fmode == MCAST_UNDEFINED) {
                          CTR1(KTR_MLD, "%s: final leave", __func__);
                          mld_final_leave(inm, mli);
                          goto out_locked;
                  }
          } else {
                  CTR1(KTR_MLD, "%s: filter set change", __func__);
          }
  
          error = mld_handle_state_change(inm, mli);
  
  out_locked:
          MLD_UNLOCK();
          return (error);
  }
  
  /*
   * Perform the initial join for an MLD group.
   *
   * When joining a group:
   *  If the group should have its MLD traffic suppressed, do nothing.
   *  MLDv1 starts sending MLDv1 host membership reports.
   *  MLDv2 will schedule an MLDv2 state-change report containing the
   *  initial state of the membership.
   *
   * If the delay argument is non-zero, then we must delay sending the
   * initial state change for delay ticks (in units of MLD_FASTHZ).
   */
  static int
  mld_initial_join(struct in6_multi *inm, struct mld_ifsoftc *mli,
      const int delay)
  {
          struct epoch_tracker     et;
          struct ifnet            *ifp;
          struct mbufq            *mq;
          int                      error, retval, syncstates;
          int                      odelay;
  #ifdef KTR
          char                     ip6tbuf[INET6_ADDRSTRLEN];
  #endif
  
          CTR4(KTR_MLD, "%s: initial join %s on ifp %p(%s)",
              __func__, ip6_sprintf(ip6tbuf, &inm->in6m_addr),
              inm->in6m_ifp, if_name(inm->in6m_ifp));
  
          error = 0;
          syncstates = 1;
  
          ifp = inm->in6m_ifp;
  
          IN6_MULTI_LIST_LOCK_ASSERT();
          MLD_LOCK_ASSERT();
  
          KASSERT(mli && mli->mli_ifp == ifp, ("%s: inconsistent ifp", __func__));
  
          /*
           * Groups joined on loopback or marked as 'not reported',
           * enter the MLD_SILENT_MEMBER state and
           * are never reported in any protocol exchanges.
           * All other groups enter the appropriate state machine
           * for the version in use on this link.
           * A link marked as MLIF_SILENT causes MLD to be completely
           * disabled for the link.
           */
          if ((ifp->if_flags & IFF_LOOPBACK) ||
              (mli->mli_flags & MLIF_SILENT) ||
              !mld_is_addr_reported(&inm->in6m_addr)) {
                  CTR1(KTR_MLD,
  "%s: not kicking state machine for silent group", __func__);
                  inm->in6m_state = MLD_SILENT_MEMBER;
                  inm->in6m_timer = 0;
          } else {
                  /*
                   * Deal with overlapping in_multi lifecycle.
                   * If this group was LEAVING, then make sure
                   * we drop the reference we picked up to keep the
                   * group around for the final INCLUDE {} enqueue.
                   */
                  if (mli->mli_version == MLD_VERSION_2 &&
                      inm->in6m_state == MLD_LEAVING_MEMBER) {
                          inm->in6m_refcount--;
                          MPASS(inm->in6m_refcount > 0);
                  }
                  inm->in6m_state = MLD_REPORTING_MEMBER;
  
                  switch (mli->mli_version) {
                  case MLD_VERSION_1:
                          /*
                           * If a delay was provided, only use it if
                           * it is greater than the delay normally
                           * used for an MLDv1 state change report,
                           * and delay sending the initial MLDv1 report
                           * by not transitioning to the IDLE state.
                           */
                          odelay = MLD_RANDOM_DELAY(MLD_V1_MAX_RI * MLD_FASTHZ);
                          if (delay) {
                                  inm->in6m_timer = max(delay, odelay);
                                  V_current_state_timers_running6 = 1;
                          } else {
                                  inm->in6m_state = MLD_IDLE_MEMBER;
                                  NET_EPOCH_ENTER(et);
                                  error = mld_v1_transmit_report(inm,
                                       MLD_LISTENER_REPORT);
                                  NET_EPOCH_EXIT(et);
                                  if (error == 0) {
                                          inm->in6m_timer = odelay;
                                          V_current_state_timers_running6 = 1;
                                  }
                          }
                          break;
  
                  case MLD_VERSION_2:
                          /*
                           * Defer update of T0 to T1, until the first copy
                           * of the state change has been transmitted.
                           */
                          syncstates = 0;
  
                          /*
                           * Immediately enqueue a State-Change Report for
                           * this interface, freeing any previous reports.
                           * Don't kick the timers if there is nothing to do,
                           * or if an error occurred.
                           */
                          mq = &inm->in6m_scq;
                          mbufq_drain(mq);
                          retval = mld_v2_enqueue_group_record(mq, inm, 1,
                              0, 0, (mli->mli_flags & MLIF_USEALLOW));
                          CTR2(KTR_MLD, "%s: enqueue record = %d",
                              __func__, retval);
                          if (retval <= 0) {
                                  error = retval * -1;
                                  break;
                          }
  
                          /*
                           * Schedule transmission of pending state-change
                           * report up to RV times for this link. The timer
                           * will fire at the next mld_fasttimo (~200ms),
                           * giving us an opportunity to merge the reports.
                           *
                           * If a delay was provided to this function, only
                           * use this delay if sooner than the existing one.
                           */
                          KASSERT(mli->mli_rv > 1,
                             ("%s: invalid robustness %d", __func__,
                              mli->mli_rv));
                          inm->in6m_scrv = mli->mli_rv;
                          if (delay) {
                                  if (inm->in6m_sctimer > 1) {
                                          inm->in6m_sctimer =
                                              min(inm->in6m_sctimer, delay);
                                  } else
                                          inm->in6m_sctimer = delay;
                          } else
                                  inm->in6m_sctimer = 1;
                          V_state_change_timers_running6 = 1;
  
                          error = 0;
                          break;
                  }
          }
  
          /*
           * Only update the T0 state if state change is atomic,
           * i.e. we don't need to wait for a timer to fire before we
           * can consider the state change to have been communicated.
           */
          if (syncstates) {
                  in6m_commit(inm);
                  CTR3(KTR_MLD, "%s: T1 -> T0 for %s/%s", __func__,
                      ip6_sprintf(ip6tbuf, &inm->in6m_addr),
                      if_name(inm->in6m_ifp));
          }
  
          return (error);
  }
  
  /*
   * Issue an intermediate state change during the life-cycle.
   */
  static int
  mld_handle_state_change(struct in6_multi *inm, struct mld_ifsoftc *mli)
  {
          struct ifnet            *ifp;
          int                      retval;
  #ifdef KTR
          char                     ip6tbuf[INET6_ADDRSTRLEN];
  #endif
  
          CTR4(KTR_MLD, "%s: state change for %s on ifp %p(%s)",
              __func__, ip6_sprintf(ip6tbuf, &inm->in6m_addr),
              inm->in6m_ifp, if_name(inm->in6m_ifp));
  
          ifp = inm->in6m_ifp;
  
          IN6_MULTI_LIST_LOCK_ASSERT();
          MLD_LOCK_ASSERT();
  
          KASSERT(mli && mli->mli_ifp == ifp,
              ("%s: inconsistent ifp", __func__));
  
          if ((ifp->if_flags & IFF_LOOPBACK) ||
              (mli->mli_flags & MLIF_SILENT) ||
              !mld_is_addr_reported(&inm->in6m_addr) ||
              (mli->mli_version != MLD_VERSION_2)) {
                  if (!mld_is_addr_reported(&inm->in6m_addr)) {
                          CTR1(KTR_MLD,
  "%s: not kicking state machine for silent group", __func__);
                  }
                  CTR1(KTR_MLD, "%s: nothing to do", __func__);
                  in6m_commit(inm);
                  CTR3(KTR_MLD, "%s: T1 -> T0 for %s/%s", __func__,
                      ip6_sprintf(ip6tbuf, &inm->in6m_addr),
                      if_name(inm->in6m_ifp));
                  return (0);
          }
  
          mbufq_drain(&inm->in6m_scq);
  
          retval = mld_v2_enqueue_group_record(&inm->in6m_scq, inm, 1, 0, 0,
              (mli->mli_flags & MLIF_USEALLOW));
          CTR2(KTR_MLD, "%s: enqueue record = %d", __func__, retval);
          if (retval <= 0)
                  return (-retval);
  
          /*
           * If record(s) were enqueued, start the state-change
           * report timer for this group.
           */
          inm->in6m_scrv = mli->mli_rv;
          inm->in6m_sctimer = 1;
          V_state_change_timers_running6 = 1;
  
          return (0);
  }
  
  /*
   * Perform the final leave for a multicast address.
   *
   * When leaving a group:
   *  MLDv1 sends a DONE message, if and only if we are the reporter.
   *  MLDv2 enqueues a state-change report containing a transition
   *  to INCLUDE {} for immediate transmission.
   */
  static void
  mld_final_leave(struct in6_multi *inm, struct mld_ifsoftc *mli)
  {
          struct epoch_tracker     et;
          int syncstates;
  #ifdef KTR
          char ip6tbuf[INET6_ADDRSTRLEN];
  #endif
  
          syncstates = 1;
  
          CTR4(KTR_MLD, "%s: final leave %s on ifp %p(%s)",
              __func__, ip6_sprintf(ip6tbuf, &inm->in6m_addr),
              inm->in6m_ifp, if_name(inm->in6m_ifp));
  
          IN6_MULTI_LIST_LOCK_ASSERT();
          MLD_LOCK_ASSERT();
  
          switch (inm->in6m_state) {
          case MLD_NOT_MEMBER:
          case MLD_SILENT_MEMBER:
          case MLD_LEAVING_MEMBER:
                  /* Already leaving or left; do nothing. */
                  CTR1(KTR_MLD,
  "%s: not kicking state machine for silent group", __func__);
                  break;
          case MLD_REPORTING_MEMBER:
          case MLD_IDLE_MEMBER:
          case MLD_G_QUERY_PENDING_MEMBER:
          case MLD_SG_QUERY_PENDING_MEMBER:
                  if (mli->mli_version == MLD_VERSION_1) {
  #ifdef INVARIANTS
                          if (inm->in6m_state == MLD_G_QUERY_PENDING_MEMBER ||
                              inm->in6m_state == MLD_SG_QUERY_PENDING_MEMBER)
                          panic("%s: MLDv2 state reached, not MLDv2 mode",
                               __func__);
  #endif
                          NET_EPOCH_ENTER(et);
                          mld_v1_transmit_report(inm, MLD_LISTENER_DONE);
                          NET_EPOCH_EXIT(et);
                          inm->in6m_state = MLD_NOT_MEMBER;
                          V_current_state_timers_running6 = 1;
                  } else if (mli->mli_version == MLD_VERSION_2) {
                          /*
                           * Stop group timer and all pending reports.
                           * Immediately enqueue a state-change report
                           * TO_IN {} to be sent on the next fast timeout,
                           * giving us an opportunity to merge reports.
                           */
                          mbufq_drain(&inm->in6m_scq);
                          inm->in6m_timer = 0;
                          inm->in6m_scrv = mli->mli_rv;
                          CTR4(KTR_MLD, "%s: Leaving %s/%s with %d "
                              "pending retransmissions.", __func__,
                              ip6_sprintf(ip6tbuf, &inm->in6m_addr),
                              if_name(inm->in6m_ifp), inm->in6m_scrv);
                          if (inm->in6m_scrv == 0) {
                                  inm->in6m_state = MLD_NOT_MEMBER;
                                  inm->in6m_sctimer = 0;
                          } else {
                                  int retval __diagused;
  
                                  in6m_acquire_locked(inm);
  
                                  retval = mld_v2_enqueue_group_record(
                                      &inm->in6m_scq, inm, 1, 0, 0,
                                      (mli->mli_flags & MLIF_USEALLOW));
                                  KASSERT(retval != 0,
                                      ("%s: enqueue record = %d", __func__,
                                       retval));
  
                                  inm->in6m_state = MLD_LEAVING_MEMBER;
                                  inm->in6m_sctimer = 1;
                                  V_state_change_timers_running6 = 1;
                                  syncstates = 0;
                          }
                          break;
                  }
                  break;
          case MLD_LAZY_MEMBER:
          case MLD_SLEEPING_MEMBER:
          case MLD_AWAKENING_MEMBER:
                  /* Our reports are suppressed; do nothing. */
                  break;
          }
  
          if (syncstates) {
                  in6m_commit(inm);
                  CTR3(KTR_MLD, "%s: T1 -> T0 for %s/%s", __func__,
                      ip6_sprintf(ip6tbuf, &inm->in6m_addr),
                      if_name(inm->in6m_ifp));
                  inm->in6m_st[1].iss_fmode = MCAST_UNDEFINED;
                  CTR3(KTR_MLD, "%s: T1 now MCAST_UNDEFINED for %p/%s",
                      __func__, &inm->in6m_addr, if_name(inm->in6m_ifp));
          }
  }
  
  /*
   * Enqueue an MLDv2 group record to the given output queue.
   *
   * If is_state_change is zero, a current-state record is appended.
   * If is_state_change is non-zero, a state-change report is appended.
   *
   * If is_group_query is non-zero, an mbuf packet chain is allocated.
   * If is_group_query is zero, and if there is a packet with free space
   * at the tail of the queue, it will be appended to providing there
   * is enough free space.
   * Otherwise a new mbuf packet chain is allocated.
   *
   * If is_source_query is non-zero, each source is checked to see if
   * it was recorded for a Group-Source query, and will be omitted if
   * it is not both in-mode and recorded.
   *
   * If use_block_allow is non-zero, state change reports for initial join
   * and final leave, on an inclusive mode group with a source list, will be
   * rewritten to use the ALLOW_NEW and BLOCK_OLD record types, respectively.
   *
   * The function will attempt to allocate leading space in the packet
   * for the IPv6+ICMP headers to be prepended without fragmenting the chain.
   *
   * If successful the size of all data appended to the queue is returned,
   * otherwise an error code less than zero is returned, or zero if
   * no record(s) were appended.
   */
  static int
  mld_v2_enqueue_group_record(struct mbufq *mq, struct in6_multi *inm,
      const int is_state_change, const int is_group_query,
      const int is_source_query, const int use_block_allow)
  {
          struct mldv2_record      mr;
          struct mldv2_record     *pmr;
          struct ifnet            *ifp;
          struct ip6_msource      *ims, *nims;
          struct mbuf             *m0, *m, *md;
          int                      is_filter_list_change;
          int                      minrec0len, m0srcs, msrcs, nbytes, off;
          int                      record_has_sources;
          int                      now;
          int                      type;
          uint8_t                  mode;
  #ifdef KTR
          char                     ip6tbuf[INET6_ADDRSTRLEN];
  #endif
  
          IN6_MULTI_LIST_LOCK_ASSERT();
  
          ifp = inm->in6m_ifp;
          is_filter_list_change = 0;
          m = NULL;
          m0 = NULL;
          m0srcs = 0;
          msrcs = 0;
          nbytes = 0;
          nims = NULL;
          record_has_sources = 1;
          pmr = NULL;
          type = MLD_DO_NOTHING;
          mode = inm->in6m_st[1].iss_fmode;
  
          /*
           * If we did not transition out of ASM mode during t0->t1,
           * and there are no source nodes to process, we can skip
           * the generation of source records.
           */
          if (inm->in6m_st[0].iss_asm > 0 && inm->in6m_st[1].iss_asm > 0 &&
              inm->in6m_nsrc == 0)
                  record_has_sources = 0;
  
          if (is_state_change) {
                  /*
                   * Queue a state change record.
                   * If the mode did not change, and there are non-ASM
                   * listeners or source filters present,
                   * we potentially need to issue two records for the group.
                   * If there are ASM listeners, and there was no filter
                   * mode transition of any kind, do nothing.
                   *
                   * If we are transitioning to MCAST_UNDEFINED, we need
                   * not send any sources. A transition to/from this state is
                   * considered inclusive with some special treatment.
                   *
                   * If we are rewriting initial joins/leaves to use
                   * ALLOW/BLOCK, and the group's membership is inclusive,
                   * we need to send sources in all cases.
                   */
                  if (mode != inm->in6m_st[0].iss_fmode) {
                          if (mode == MCAST_EXCLUDE) {
                                  CTR1(KTR_MLD, "%s: change to EXCLUDE",
                                      __func__);
                                  type = MLD_CHANGE_TO_EXCLUDE_MODE;
                          } else {
                                  CTR1(KTR_MLD, "%s: change to INCLUDE",
                                      __func__);
                                  if (use_block_allow) {
                                          /*
                                           * XXX
                                           * Here we're interested in state
                                           * edges either direction between
                                           * MCAST_UNDEFINED and MCAST_INCLUDE.
                                           * Perhaps we should just check
                                           * the group state, rather than
                                           * the filter mode.
                                           */
                                          if (mode == MCAST_UNDEFINED) {
                                                  type = MLD_BLOCK_OLD_SOURCES;
                                          } else {
                                                  type = MLD_ALLOW_NEW_SOURCES;
                                          }
                                  } else {
                                          type = MLD_CHANGE_TO_INCLUDE_MODE;
                                          if (mode == MCAST_UNDEFINED)
                                                  record_has_sources = 0;
                                  }
                          }
                  } else {
                          if (record_has_sources) {
                                  is_filter_list_change = 1;
                          } else {
                                  type = MLD_DO_NOTHING;
                          }
                  }
          } else {
                  /*
                   * Queue a current state record.
                   */
                  if (mode == MCAST_EXCLUDE) {
                          type = MLD_MODE_IS_EXCLUDE;
                  } else if (mode == MCAST_INCLUDE) {
                          type = MLD_MODE_IS_INCLUDE;
                          KASSERT(inm->in6m_st[1].iss_asm == 0,
                              ("%s: inm %p is INCLUDE but ASM count is %d",
                               __func__, inm, inm->in6m_st[1].iss_asm));
                  }
          }
  
          /*
           * Generate the filter list changes using a separate function.
           */
          if (is_filter_list_change)
                  return (mld_v2_enqueue_filter_change(mq, inm));
  
          if (type == MLD_DO_NOTHING) {
                  CTR3(KTR_MLD, "%s: nothing to do for %s/%s",
                      __func__, ip6_sprintf(ip6tbuf, &inm->in6m_addr),
                      if_name(inm->in6m_ifp));
                  return (0);
          }
  
          /*
           * If any sources are present, we must be able to fit at least
           * one in the trailing space of the tail packet's mbuf,
           * ideally more.
           */
          minrec0len = sizeof(struct mldv2_record);
          if (record_has_sources)
                  minrec0len += sizeof(struct in6_addr);
  
          CTR4(KTR_MLD, "%s: queueing %s for %s/%s", __func__,
              mld_rec_type_to_str(type),
              ip6_sprintf(ip6tbuf, &inm->in6m_addr),
              if_name(inm->in6m_ifp));
  
          /*
           * Check if we have a packet in the tail of the queue for this
           * group into which the first group record for this group will fit.
           * Otherwise allocate a new packet.
           * Always allocate leading space for IP6+RA+ICMPV6+REPORT.
           * Note: Group records for G/GSR query responses MUST be sent
           * in their own packet.
           */
          m0 = mbufq_last(mq);
          if (!is_group_query &&
              m0 != NULL &&
              (m0->m_pkthdr.vt_nrecs + 1 <= MLD_V2_REPORT_MAXRECS) &&
              (m0->m_pkthdr.len + minrec0len) <
               (ifp->if_mtu - MLD_MTUSPACE)) {
                  m0srcs = (ifp->if_mtu - m0->m_pkthdr.len -
                              sizeof(struct mldv2_record)) /
                              sizeof(struct in6_addr);
                  m = m0;
                  CTR1(KTR_MLD, "%s: use existing packet", __func__);
          } else {
                  if (mbufq_full(mq)) {
                          CTR1(KTR_MLD, "%s: outbound queue full", __func__);
                          return (-ENOMEM);
                  }
                  m = NULL;
                  m0srcs = (ifp->if_mtu - MLD_MTUSPACE -
                      sizeof(struct mldv2_record)) / sizeof(struct in6_addr);
                  if (!is_state_change && !is_group_query)
                          m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
                  if (m == NULL)
                          m = m_gethdr(M_NOWAIT, MT_DATA);
                  if (m == NULL)
                          return (-ENOMEM);
  
                  mld_save_context(m, ifp);
  
                  CTR1(KTR_MLD, "%s: allocated first packet", __func__);
          }
  
          /*
           * Append group record.
           * If we have sources, we don't know how many yet.
           */
          mr.mr_type = type;
          mr.mr_datalen = 0;
          mr.mr_numsrc = 0;
          mr.mr_addr = inm->in6m_addr;
          in6_clearscope(&mr.mr_addr);
          if (!m_append(m, sizeof(struct mldv2_record), (void *)&mr)) {
                  if (m != m0)
                          m_freem(m);
                  CTR1(KTR_MLD, "%s: m_append() failed.", __func__);
                  return (-ENOMEM);
          }
          nbytes += sizeof(struct mldv2_record);
  
          /*
           * Append as many sources as will fit in the first packet.
           * If we are appending to a new packet, the chain allocation
           * may potentially use clusters; use m_getptr() in this case.
           * If we are appending to an existing packet, we need to obtain
           * a pointer to the group record after m_append(), in case a new
           * mbuf was allocated.
           *
           * Only append sources which are in-mode at t1. If we are
           * transitioning to MCAST_UNDEFINED state on the group, and
           * use_block_allow is zero, do not include source entries.
           * Otherwise, we need to include this source in the report.
           *
           * Only report recorded sources in our filter set when responding
           * to a group-source query.
           */
          if (record_has_sources) {
                  if (m == m0) {
                          md = m_last(m);
                          pmr = (struct mldv2_record *)(mtod(md, uint8_t *) +
                              md->m_len - nbytes);
                  } else {
                          md = m_getptr(m, 0, &off);
                          pmr = (struct mldv2_record *)(mtod(md, uint8_t *) +
                              off);
                  }
                  msrcs = 0;
                  RB_FOREACH_SAFE(ims, ip6_msource_tree, &inm->in6m_srcs,
                      nims) {
                          CTR2(KTR_MLD, "%s: visit node %s", __func__,
                              ip6_sprintf(ip6tbuf, &ims->im6s_addr));
                          now = im6s_get_mode(inm, ims, 1);
                          CTR2(KTR_MLD, "%s: node is %d", __func__, now);
                          if ((now != mode) ||
                              (now == mode &&
                               (!use_block_allow && mode == MCAST_UNDEFINED))) {
                                  CTR1(KTR_MLD, "%s: skip node", __func__);
                                  continue;
                          }
                          if (is_source_query && ims->im6s_stp == 0) {
                                  CTR1(KTR_MLD, "%s: skip unrecorded node",
                                      __func__);
                                  continue;
                          }
                          CTR1(KTR_MLD, "%s: append node", __func__);
                          if (!m_append(m, sizeof(struct in6_addr),
                              (void *)&ims->im6s_addr)) {
                                  if (m != m0)
                                          m_freem(m);
                                  CTR1(KTR_MLD, "%s: m_append() failed.",
                                      __func__);
                                  return (-ENOMEM);
                          }
                          nbytes += sizeof(struct in6_addr);
                          ++msrcs;
                          if (msrcs == m0srcs)
                                  break;
                  }
                  CTR2(KTR_MLD, "%s: msrcs is %d this packet", __func__,
                      msrcs);
                  pmr->mr_numsrc = htons(msrcs);
                  nbytes += (msrcs * sizeof(struct in6_addr));
          }
  
          if (is_source_query && msrcs == 0) {
                  CTR1(KTR_MLD, "%s: no recorded sources to report", __func__);
                  if (m != m0)
                          m_freem(m);
                  return (0);
          }
  
          /*
           * We are good to go with first packet.
           */
          if (m != m0) {
                  CTR1(KTR_MLD, "%s: enqueueing first packet", __func__);
                  m->m_pkthdr.vt_nrecs = 1;
                  mbufq_enqueue(mq, m);
          } else
                  m->m_pkthdr.vt_nrecs++;
  
          /*
           * No further work needed if no source list in packet(s).
           */
          if (!record_has_sources)
                  return (nbytes);
  
          /*
           * Whilst sources remain to be announced, we need to allocate
           * a new packet and fill out as many sources as will fit.
           * Always try for a cluster first.
           */
          while (nims != NULL) {
                  if (mbufq_full(mq)) {
                          CTR1(KTR_MLD, "%s: outbound queue full", __func__);
                          return (-ENOMEM);
                  }
                  m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
                  if (m == NULL)
                          m = m_gethdr(M_NOWAIT, MT_DATA);
                  if (m == NULL)
                          return (-ENOMEM);
                  mld_save_context(m, ifp);
                  md = m_getptr(m, 0, &off);
                  pmr = (struct mldv2_record *)(mtod(md, uint8_t *) + off);
                  CTR1(KTR_MLD, "%s: allocated next packet", __func__);
  
                  if (!m_append(m, sizeof(struct mldv2_record), (void *)&mr)) {
                          if (m != m0)
                                  m_freem(m);
                          CTR1(KTR_MLD, "%s: m_append() failed.", __func__);
                          return (-ENOMEM);
                  }
                  m->m_pkthdr.vt_nrecs = 1;
                  nbytes += sizeof(struct mldv2_record);
  
                  m0srcs = (ifp->if_mtu - MLD_MTUSPACE -
                      sizeof(struct mldv2_record)) / sizeof(struct in6_addr);
  
                  msrcs = 0;
                  RB_FOREACH_FROM(ims, ip6_msource_tree, nims) {
                          CTR2(KTR_MLD, "%s: visit node %s",
                              __func__, ip6_sprintf(ip6tbuf, &ims->im6s_addr));
                          now = im6s_get_mode(inm, ims, 1);
                          if ((now != mode) ||
                              (now == mode &&
                               (!use_block_allow && mode == MCAST_UNDEFINED))) {
                                  CTR1(KTR_MLD, "%s: skip node", __func__);
                                  continue;
                          }
                          if (is_source_query && ims->im6s_stp == 0) {
                                  CTR1(KTR_MLD, "%s: skip unrecorded node",
                                      __func__);
                                  continue;
                          }
                          CTR1(KTR_MLD, "%s: append node", __func__);
                          if (!m_append(m, sizeof(struct in6_addr),
                              (void *)&ims->im6s_addr)) {
                                  if (m != m0)
                                          m_freem(m);
                                  CTR1(KTR_MLD, "%s: m_append() failed.",
                                      __func__);
                                  return (-ENOMEM);
                          }
                          ++msrcs;
                          if (msrcs == m0srcs)
                                  break;
                  }
                  pmr->mr_numsrc = htons(msrcs);
                  nbytes += (msrcs * sizeof(struct in6_addr));
  
                  CTR1(KTR_MLD, "%s: enqueueing next packet", __func__);
                  mbufq_enqueue(mq, m);
          }
  
          return (nbytes);
  }
  
  /*
   * Type used to mark record pass completion.
   * We exploit the fact we can cast to this easily from the
   * current filter modes on each ip_msource node.
   */
  typedef enum {
          REC_NONE = 0x00,        /* MCAST_UNDEFINED */
          REC_ALLOW = 0x01,       /* MCAST_INCLUDE */
          REC_BLOCK = 0x02,       /* MCAST_EXCLUDE */
          REC_FULL = REC_ALLOW | REC_BLOCK
  } rectype_t;
  
  /*
   * Enqueue an MLDv2 filter list change to the given output queue.
   *
   * Source list filter state is held in an RB-tree. When the filter list
   * for a group is changed without changing its mode, we need to compute
   * the deltas between T0 and T1 for each source in the filter set,
   * and enqueue the appropriate ALLOW_NEW/BLOCK_OLD records.
   *
   * As we may potentially queue two record types, and the entire R-B tree
   * needs to be walked at once, we break this out into its own function
   * so we can generate a tightly packed queue of packets.
   *
   * XXX This could be written to only use one tree walk, although that makes
   * serializing into the mbuf chains a bit harder. For now we do two walks
   * which makes things easier on us, and it may or may not be harder on
   * the L2 cache.
   *
   * If successful the size of all data appended to the queue is returned,
   * otherwise an error code less than zero is returned, or zero if
   * no record(s) were appended.
   */
  static int
  mld_v2_enqueue_filter_change(struct mbufq *mq, struct in6_multi *inm)
  {
          static const int MINRECLEN =
              sizeof(struct mldv2_record) + sizeof(struct in6_addr);
          struct ifnet            *ifp;
          struct mldv2_record      mr;
          struct mldv2_record     *pmr;
          struct ip6_msource      *ims, *nims;
          struct mbuf             *m, *m0, *md;
          int                      m0srcs, nbytes, npbytes, off, rsrcs, schanged;
          uint8_t                  mode, now, then;
          rectype_t                crt, drt, nrt;
  #ifdef KTR
          int                      nallow, nblock;
          char                     ip6tbuf[INET6_ADDRSTRLEN];
  #endif
  
          IN6_MULTI_LIST_LOCK_ASSERT();
  
          if (inm->in6m_nsrc == 0 ||
              (inm->in6m_st[0].iss_asm > 0 && inm->in6m_st[1].iss_asm > 0))
                  return (0);
  
          ifp = inm->in6m_ifp;                    /* interface */
          mode = inm->in6m_st[1].iss_fmode;       /* filter mode at t1 */
          crt = REC_NONE; /* current group record type */
          drt = REC_NONE; /* mask of completed group record types */
          nrt = REC_NONE; /* record type for current node */
          m0srcs = 0;     /* # source which will fit in current mbuf chain */
          npbytes = 0;    /* # of bytes appended this packet */
          nbytes = 0;     /* # of bytes appended to group's state-change queue */
          rsrcs = 0;      /* # sources encoded in current record */
          schanged = 0;   /* # nodes encoded in overall filter change */
  #ifdef KTR
          nallow = 0;     /* # of source entries in ALLOW_NEW */
          nblock = 0;     /* # of source entries in BLOCK_OLD */
  #endif
          nims = NULL;    /* next tree node pointer */
  
          /*
           * For each possible filter record mode.
           * The first kind of source we encounter tells us which
           * is the first kind of record we start appending.
           * If a node transitioned to UNDEFINED at t1, its mode is treated
           * as the inverse of the group's filter mode.
           */
          while (drt != REC_FULL) {
                  do {
                          m0 = mbufq_last(mq);
                          if (m0 != NULL &&
                              (m0->m_pkthdr.vt_nrecs + 1 <=
                               MLD_V2_REPORT_MAXRECS) &&
                              (m0->m_pkthdr.len + MINRECLEN) <
                               (ifp->if_mtu - MLD_MTUSPACE)) {
                                  m = m0;
                                  m0srcs = (ifp->if_mtu - m0->m_pkthdr.len -
                                              sizeof(struct mldv2_record)) /
                                              sizeof(struct in6_addr);
                                  CTR1(KTR_MLD,
                                      "%s: use previous packet", __func__);
                          } else {
                                  m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
                                  if (m == NULL)
                                          m = m_gethdr(M_NOWAIT, MT_DATA);
                                  if (m == NULL) {
                                          CTR1(KTR_MLD,
                                              "%s: m_get*() failed", __func__);
                                          return (-ENOMEM);
                                  }
                                  m->m_pkthdr.vt_nrecs = 0;
                                  mld_save_context(m, ifp);
                                  m0srcs = (ifp->if_mtu - MLD_MTUSPACE -
                                      sizeof(struct mldv2_record)) /
                                      sizeof(struct in6_addr);
                                  npbytes = 0;
                                  CTR1(KTR_MLD,
                                      "%s: allocated new packet", __func__);
                          }
                          /*
                           * Append the MLD group record header to the
                           * current packet's data area.
                           * Recalculate pointer to free space for next
                           * group record, in case m_append() allocated
                           * a new mbuf or cluster.
                           */
                          memset(&mr, 0, sizeof(mr));
                          mr.mr_addr = inm->in6m_addr;
                          in6_clearscope(&mr.mr_addr);
                          if (!m_append(m, sizeof(mr), (void *)&mr)) {
                                  if (m != m0)
                                          m_freem(m);
                                  CTR1(KTR_MLD,
                                      "%s: m_append() failed", __func__);
                                  return (-ENOMEM);
                          }
                          npbytes += sizeof(struct mldv2_record);
                          if (m != m0) {
                                  /* new packet; offset in chain */
                                  md = m_getptr(m, npbytes -
                                      sizeof(struct mldv2_record), &off);
                                  pmr = (struct mldv2_record *)(mtod(md,
                                      uint8_t *) + off);
                          } else {
                                  /* current packet; offset from last append */
                                  md = m_last(m);
                                  pmr = (struct mldv2_record *)(mtod(md,
                                      uint8_t *) + md->m_len -
                                      sizeof(struct mldv2_record));
                          }
                          /*
                           * Begin walking the tree for this record type
                           * pass, or continue from where we left off
                           * previously if we had to allocate a new packet.
                           * Only report deltas in-mode at t1.
                           * We need not report included sources as allowed
                           * if we are in inclusive mode on the group,
                           * however the converse is not true.
                           */
                          rsrcs = 0;
                          if (nims == NULL) {
                                  nims = RB_MIN(ip6_msource_tree,
                                      &inm->in6m_srcs);
                          }
                          RB_FOREACH_FROM(ims, ip6_msource_tree, nims) {
                                  CTR2(KTR_MLD, "%s: visit node %s", __func__,
                                      ip6_sprintf(ip6tbuf, &ims->im6s_addr));
                                  now = im6s_get_mode(inm, ims, 1);
                                  then = im6s_get_mode(inm, ims, 0);
                                  CTR3(KTR_MLD, "%s: mode: t0 %d, t1 %d",
                                      __func__, then, now);
                                  if (now == then) {
                                          CTR1(KTR_MLD,
                                              "%s: skip unchanged", __func__);
                                          continue;
                                  }
                                  if (mode == MCAST_EXCLUDE &&
                                      now == MCAST_INCLUDE) {
                                          CTR1(KTR_MLD,
                                              "%s: skip IN src on EX group",
                                              __func__);
                                          continue;
                                  }
                                  nrt = (rectype_t)now;
                                  if (nrt == REC_NONE)
                                          nrt = (rectype_t)(~mode & REC_FULL);
                                  if (schanged++ == 0) {
                                          crt = nrt;
                                  } else if (crt != nrt)
                                          continue;
                                  if (!m_append(m, sizeof(struct in6_addr),
                                      (void *)&ims->im6s_addr)) {
                                          if (m != m0)
                                                  m_freem(m);
                                          CTR1(KTR_MLD,
                                              "%s: m_append() failed", __func__);
                                          return (-ENOMEM);
                                  }
  #ifdef KTR
                                  nallow += !!(crt == REC_ALLOW);
                                  nblock += !!(crt == REC_BLOCK);
  #endif
                                  if (++rsrcs == m0srcs)
                                          break;
                          }
                          /*
                           * If we did not append any tree nodes on this
                           * pass, back out of allocations.
                           */
                          if (rsrcs == 0) {
                                  npbytes -= sizeof(struct mldv2_record);
                                  if (m != m0) {
                                          CTR1(KTR_MLD,
                                              "%s: m_free(m)", __func__);
                                          m_freem(m);
                                  } else {
                                          CTR1(KTR_MLD,
                                              "%s: m_adj(m, -mr)", __func__);
                                          m_adj(m, -((int)sizeof(
                                              struct mldv2_record)));
                                  }
                                  continue;
                          }
                          npbytes += (rsrcs * sizeof(struct in6_addr));
                          if (crt == REC_ALLOW)
                                  pmr->mr_type = MLD_ALLOW_NEW_SOURCES;
                          else if (crt == REC_BLOCK)
                                  pmr->mr_type = MLD_BLOCK_OLD_SOURCES;
                          pmr->mr_numsrc = htons(rsrcs);
                          /*
                           * Count the new group record, and enqueue this
                           * packet if it wasn't already queued.
                           */
                          m->m_pkthdr.vt_nrecs++;
                          if (m != m0)
                                  mbufq_enqueue(mq, m);
                          nbytes += npbytes;
                  } while (nims != NULL);
                  drt |= crt;
                  crt = (~crt & REC_FULL);
          }
  
          CTR3(KTR_MLD, "%s: queued %d ALLOW_NEW, %d BLOCK_OLD", __func__,
              nallow, nblock);
  
          return (nbytes);
  }
  
  static int
  mld_v2_merge_state_changes(struct in6_multi *inm, struct mbufq *scq)
  {
          struct mbufq    *gq;
          struct mbuf     *m;             /* pending state-change */
          struct mbuf     *m0;            /* copy of pending state-change */
          struct mbuf     *mt;            /* last state-change in packet */
          int              docopy, domerge;
          u_int            recslen;
  
          docopy = 0;
          domerge = 0;
          recslen = 0;
  
          IN6_MULTI_LIST_LOCK_ASSERT();
          MLD_LOCK_ASSERT();
  
          /*
           * If there are further pending retransmissions, make a writable
           * copy of each queued state-change message before merging.
           */
          if (inm->in6m_scrv > 0)
                  docopy = 1;
  
          gq = &inm->in6m_scq;
  #ifdef KTR
          if (mbufq_first(gq) == NULL) {
                  CTR2(KTR_MLD, "%s: WARNING: queue for inm %p is empty",
                      __func__, inm);
          }
  #endif
  
          m = mbufq_first(gq);
          while (m != NULL) {
                  /*
                   * Only merge the report into the current packet if
                   * there is sufficient space to do so; an MLDv2 report
                   * packet may only contain 65,535 group records.
                   * Always use a simple mbuf chain concatentation to do this,
                   * as large state changes for single groups may have
                   * allocated clusters.
                   */
                  domerge = 0;
                  mt = mbufq_last(scq);
                  if (mt != NULL) {
                          recslen = m_length(m, NULL);
  
                          if ((mt->m_pkthdr.vt_nrecs +
                              m->m_pkthdr.vt_nrecs <=
                              MLD_V2_REPORT_MAXRECS) &&
                              (mt->m_pkthdr.len + recslen <=
                              (inm->in6m_ifp->if_mtu - MLD_MTUSPACE)))
                                  domerge = 1;
                  }
  
                  if (!domerge && mbufq_full(gq)) {
                          CTR2(KTR_MLD,
                              "%s: outbound queue full, skipping whole packet %p",
                              __func__, m);
                          mt = m->m_nextpkt;
                          if (!docopy)
                                  m_freem(m);
                          m = mt;
                          continue;
                  }
  
                  if (!docopy) {
                          CTR2(KTR_MLD, "%s: dequeueing %p", __func__, m);
                          m0 = mbufq_dequeue(gq);
                          m = m0->m_nextpkt;
                  } else {
                          CTR2(KTR_MLD, "%s: copying %p", __func__, m);
                          m0 = m_dup(m, M_NOWAIT);
                          if (m0 == NULL)
                                  return (ENOMEM);
                          m0->m_nextpkt = NULL;
                          m = m->m_nextpkt;
                  }
  
                  if (!domerge) {
                          CTR3(KTR_MLD, "%s: queueing %p to scq %p)",
                              __func__, m0, scq);
                          mbufq_enqueue(scq, m0);
                  } else {
                          struct mbuf *mtl;       /* last mbuf of packet mt */
  
                          CTR3(KTR_MLD, "%s: merging %p with ifscq tail %p)",
                              __func__, m0, mt);
  
                          mtl = m_last(mt);
                          m0->m_flags &= ~M_PKTHDR;
                          mt->m_pkthdr.len += recslen;
                          mt->m_pkthdr.vt_nrecs +=
                              m0->m_pkthdr.vt_nrecs;
  
                          mtl->m_next = m0;
                  }
          }
  
          return (0);
  }
  
  /*
   * Respond to a pending MLDv2 General Query.
   */
  static void
  mld_v2_dispatch_general_query(struct mld_ifsoftc *mli)
  {
          struct ifmultiaddr      *ifma;
          struct ifnet            *ifp;
          struct in6_multi        *inm;
          int                      retval __unused;
  
          NET_EPOCH_ASSERT();
          IN6_MULTI_LIST_LOCK_ASSERT();
          MLD_LOCK_ASSERT();
  
          KASSERT(mli->mli_version == MLD_VERSION_2,
              ("%s: called when version %d", __func__, mli->mli_version));
  
          /*
           * Check that there are some packets queued. If so, send them first.
           * For large number of groups the reply to general query can take
           * many packets, we should finish sending them before starting of
           * queuing the new reply.
           */
          if (mbufq_len(&mli->mli_gq) != 0)
                  goto send;
  
          ifp = mli->mli_ifp;
  
          CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                  inm = in6m_ifmultiaddr_get_inm(ifma);
                  if (inm == NULL)
                          continue;
                  KASSERT(ifp == inm->in6m_ifp,
                      ("%s: inconsistent ifp", __func__));
  
                  switch (inm->in6m_state) {
                  case MLD_NOT_MEMBER:
                  case MLD_SILENT_MEMBER:
                          break;
                  case MLD_REPORTING_MEMBER:
                  case MLD_IDLE_MEMBER:
                  case MLD_LAZY_MEMBER:
                  case MLD_SLEEPING_MEMBER:
                  case MLD_AWAKENING_MEMBER:
                          inm->in6m_state = MLD_REPORTING_MEMBER;
                          retval = mld_v2_enqueue_group_record(&mli->mli_gq,
                              inm, 0, 0, 0, 0);
                          CTR2(KTR_MLD, "%s: enqueue record = %d",
                              __func__, retval);
                          break;
                  case MLD_G_QUERY_PENDING_MEMBER:
                  case MLD_SG_QUERY_PENDING_MEMBER:
                  case MLD_LEAVING_MEMBER:
                          break;
                  }
          }
  
  send:
          mld_dispatch_queue(&mli->mli_gq, MLD_MAX_RESPONSE_BURST);
  
          /*
           * Slew transmission of bursts over 500ms intervals.
           */
          if (mbufq_first(&mli->mli_gq) != NULL) {
                  mli->mli_v2_timer = 1 + MLD_RANDOM_DELAY(
                      MLD_RESPONSE_BURST_INTERVAL);
                  V_interface_timers_running6 = 1;
          }
  }
  
  /*
   * Transmit the next pending message in the output queue.
   *
   * VIMAGE: Needs to store/restore vnet pointer on a per-mbuf-chain basis.
   * MRT: Nothing needs to be done, as MLD traffic is always local to
   * a link and uses a link-scope multicast address.
   */
  static void
  mld_dispatch_packet(struct mbuf *m)
  {
          struct ip6_moptions      im6o;
          struct ifnet            *ifp;
          struct ifnet            *oifp;
          struct mbuf             *m0;
          struct mbuf             *md;
          struct ip6_hdr          *ip6;
          struct mld_hdr          *mld;
          int                      error;
          int                      off;
          int                      type;
          uint32_t                 ifindex;
  
          CTR2(KTR_MLD, "%s: transmit %p", __func__, m);
          NET_EPOCH_ASSERT();
  
          /*
           * Set VNET image pointer from enqueued mbuf chain
           * before doing anything else. Whilst we use interface
           * indexes to guard against interface detach, they are
           * unique to each VIMAGE and must be retrieved.
           */
          ifindex = mld_restore_context(m);
  
          /*
           * Check if the ifnet still exists. This limits the scope of
           * any race in the absence of a global ifp lock for low cost
           * (an array lookup).
           */
          ifp = ifnet_byindex(ifindex);
          if (ifp == NULL) {
                  CTR3(KTR_MLD, "%s: dropped %p as ifindex %u went away.",
                      __func__, m, ifindex);
                  m_freem(m);
                  IP6STAT_INC(ip6s_noroute);
                  goto out;
          }
  
          im6o.im6o_multicast_hlim  = 1;
          im6o.im6o_multicast_loop = (V_ip6_mrouter != NULL);
          im6o.im6o_multicast_ifp = ifp;
  
          if (m->m_flags & M_MLDV1) {
                  m0 = m;
          } else {
                  m0 = mld_v2_encap_report(ifp, m);
                  if (m0 == NULL) {
                          CTR2(KTR_MLD, "%s: dropped %p", __func__, m);
                          IP6STAT_INC(ip6s_odropped);
                          goto out;
                  }
          }
  
          mld_scrub_context(m0);
          m_clrprotoflags(m);
          m0->m_pkthdr.rcvif = V_loif;
  
          ip6 = mtod(m0, struct ip6_hdr *);
  #if 0
          (void)in6_setscope(&ip6->ip6_dst, ifp, NULL);   /* XXX LOR */
  #else
          /*
           * XXX XXX Break some KPI rules to prevent an LOR which would
           * occur if we called in6_setscope() at transmission.
           * See comments at top of file.
           */
          MLD_EMBEDSCOPE(&ip6->ip6_dst, ifp->if_index);
  #endif
  
          /*
           * Retrieve the ICMPv6 type before handoff to ip6_output(),
           * so we can bump the stats.
           */
          md = m_getptr(m0, sizeof(struct ip6_hdr), &off);
          mld = (struct mld_hdr *)(mtod(md, uint8_t *) + off);
          type = mld->mld_type;
  
          oifp = NULL;
          error = ip6_output(m0, &mld_po, NULL, IPV6_UNSPECSRC, &im6o,
              &oifp, NULL);
          if (error) {
                  CTR3(KTR_MLD, "%s: ip6_output(%p) = %d", __func__, m0, error);
                  goto out;
          }
          ICMP6STAT_INC(icp6s_outhist[type]);
          if (oifp != NULL) {
                  icmp6_ifstat_inc(oifp, ifs6_out_msg);
                  switch (type) {
                  case MLD_LISTENER_REPORT:
                  case MLDV2_LISTENER_REPORT:
                          icmp6_ifstat_inc(oifp, ifs6_out_mldreport);
                          break;
                  case MLD_LISTENER_DONE:
                          icmp6_ifstat_inc(oifp, ifs6_out_mlddone);
                          break;
                  }
          }
  out:
          return;
  }
  
  /*
   * Encapsulate an MLDv2 report.
   *
   * KAME IPv6 requires that hop-by-hop options be passed separately,
   * and that the IPv6 header be prepended in a separate mbuf.
   *
   * Returns a pointer to the new mbuf chain head, or NULL if the
   * allocation failed.
   */
  static struct mbuf *
  mld_v2_encap_report(struct ifnet *ifp, struct mbuf *m)
  {
          struct mbuf             *mh;
          struct mldv2_report     *mld;
          struct ip6_hdr          *ip6;
          struct in6_ifaddr       *ia;
          int                      mldreclen;
  
          KASSERT(ifp != NULL, ("%s: null ifp", __func__));
          KASSERT((m->m_flags & M_PKTHDR),
              ("%s: mbuf chain %p is !M_PKTHDR", __func__, m));
  
          /*
           * RFC3590: OK to send as :: or tentative during DAD.
           */
          NET_EPOCH_ASSERT();
          ia = in6ifa_ifpforlinklocal(ifp, IN6_IFF_NOTREADY|IN6_IFF_ANYCAST);
          if (ia == NULL)
                  CTR1(KTR_MLD, "%s: warning: ia is NULL", __func__);
  
          mh = m_gethdr(M_NOWAIT, MT_DATA);
          if (mh == NULL) {
                  if (ia != NULL)
                          ifa_free(&ia->ia_ifa);
                  m_freem(m);
                  return (NULL);
          }
          M_ALIGN(mh, sizeof(struct ip6_hdr) + sizeof(struct mldv2_report));
  
          mldreclen = m_length(m, NULL);
          CTR2(KTR_MLD, "%s: mldreclen is %d", __func__, mldreclen);
  
          mh->m_len = sizeof(struct ip6_hdr) + sizeof(struct mldv2_report);
          mh->m_pkthdr.len = sizeof(struct ip6_hdr) +
              sizeof(struct mldv2_report) + mldreclen;
  
          ip6 = mtod(mh, struct ip6_hdr *);
          ip6->ip6_flow = 0;
          ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
          ip6->ip6_vfc |= IPV6_VERSION;
          ip6->ip6_nxt = IPPROTO_ICMPV6;
          ip6->ip6_src = ia ? ia->ia_addr.sin6_addr : in6addr_any;
          if (ia != NULL)
                  ifa_free(&ia->ia_ifa);
          ip6->ip6_dst = in6addr_linklocal_allv2routers;
          /* scope ID will be set in netisr */
  
          mld = (struct mldv2_report *)(ip6 + 1);
          mld->mld_type = MLDV2_LISTENER_REPORT;
          mld->mld_code = 0;
          mld->mld_cksum = 0;
          mld->mld_v2_reserved = 0;
          mld->mld_v2_numrecs = htons(m->m_pkthdr.vt_nrecs);
          m->m_pkthdr.vt_nrecs = 0;
  
          mh->m_next = m;
          mld->mld_cksum = in6_cksum(mh, IPPROTO_ICMPV6,
              sizeof(struct ip6_hdr), sizeof(struct mldv2_report) + mldreclen);
          return (mh);
  }
  
  #ifdef KTR
  static char *
  mld_rec_type_to_str(const int type)
  {
  
          switch (type) {
                  case MLD_CHANGE_TO_EXCLUDE_MODE:
                          return "TO_EX";
                          break;
                  case MLD_CHANGE_TO_INCLUDE_MODE:
                          return "TO_IN";
                          break;
                  case MLD_MODE_IS_EXCLUDE:
                          return "MODE_EX";
                          break;
                  case MLD_MODE_IS_INCLUDE:
                          return "MODE_IN";
                          break;
                  case MLD_ALLOW_NEW_SOURCES:
                          return "ALLOW_NEW";
                          break;
                  case MLD_BLOCK_OLD_SOURCES:
                          return "BLOCK_OLD";
                          break;
                  default:
                          break;
          }
          return "unknown";
  }
  #endif
  
  static void
  mld_init(void *unused __unused)
  {
  
          CTR1(KTR_MLD, "%s: initializing", __func__);
          MLD_LOCK_INIT();
  
          ip6_initpktopts(&mld_po);
          mld_po.ip6po_hlim = 1;
          mld_po.ip6po_hbh = &mld_ra.hbh;
          mld_po.ip6po_prefer_tempaddr = IP6PO_TEMPADDR_NOTPREFER;
          mld_po.ip6po_flags = IP6PO_DONTFRAG;
  
          callout_init(&mldslow_callout, 1);
          callout_reset(&mldslow_callout, hz / MLD_SLOWHZ, mld_slowtimo, NULL);
          callout_init(&mldfast_callout, 1);
          callout_reset(&mldfast_callout, hz / MLD_FASTHZ, mld_fasttimo, NULL);
  }
  SYSINIT(mld_init, SI_SUB_PROTO_MC, SI_ORDER_MIDDLE, mld_init, NULL);
  
  static void
  mld_uninit(void *unused __unused)
  {
  
          CTR1(KTR_MLD, "%s: tearing down", __func__);
          callout_drain(&mldslow_callout);
          callout_drain(&mldfast_callout);
          MLD_LOCK_DESTROY();
  }
  SYSUNINIT(mld_uninit, SI_SUB_PROTO_MC, SI_ORDER_MIDDLE, mld_uninit, NULL);
  
  static void
  vnet_mld_init(const void *unused __unused)
  {
  
          CTR1(KTR_MLD, "%s: initializing", __func__);
  
          LIST_INIT(&V_mli_head);
  }
  VNET_SYSINIT(vnet_mld_init, SI_SUB_PROTO_MC, SI_ORDER_ANY, vnet_mld_init,
      NULL);
  
  static void
  vnet_mld_uninit(const void *unused __unused)
  {
  
          /* This can happen if we shutdown the network stack. */
          CTR1(KTR_MLD, "%s: tearing down", __func__);
  }
  VNET_SYSUNINIT(vnet_mld_uninit, SI_SUB_PROTO_MC, SI_ORDER_ANY, vnet_mld_uninit,
      NULL);
  
  static int
  mld_modevent(module_t mod, int type, void *unused __unused)
  {
  
      switch (type) {
      case MOD_LOAD:
      case MOD_UNLOAD:
          break;
      default:
          return (EOPNOTSUPP);
      }
      return (0);
  }
  
  static moduledata_t mld_mod = {
      "mld",
      mld_modevent,
      0
  };
  DECLARE_MODULE(mld, mld_mod, SI_SUB_PROTO_MC, SI_ORDER_ANY);

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